I never really look at how much ram a launcher takes so I can't really say on most of them. Also, I've recently redone everything on my phone with the newest ctmod that uses Xperia or something like that so this is all from memory (and my memory isn't that great ;-P) Here are a few that I've tried.
Nemus Launcher - I actually like this one a lot. There aren't really any themes as far as I can tell but I'm not usually into that. As long as I can pick my own wallpaper I'm pretty happy with that. The speed is pretty decent. The app drawer has a search function so you can quickly find an app in there if you know the name of it (love this). There are different ways to sort the app drawer like alphabetical or recently installed or recently used. Only problem here is when you install something new you have to tell it to sort the list again which can get annoying if you install a lot of stuff. If you swipe up on the dock thing at the bottom you can set whatever apps you want to be locked so they can't be launched without a password. Handy for locking the market so kids can't purchase stuff without you knowing ;-) You can also set it to hide apps from the app drawer so you can get rid of things like the SwiftKey icon and stuff like that *cough*pr0n*cough*.
Full Screen Launcher - Very very sloooooowwwww. Has some interesting concepts but it was just too slow for me so I didn't play with it so much.
Launcher 7 - Like the windows phone 7 or whatever I guess. I didn't like those big blocky buttons and it just rubbed me the wrong way so I didn't have that one very long. Guess it's cool for some but I just prefer putting icons where I want them and on what desktop I want them. I think the speed was good though.
91 Pandahome Pro - Has a lot of themes but for some reason it puts a ton of images on your sd that show up in the Gallery or Quickpro. After I saw that I got rid of it and all the images so I can't really say a lot about it. Speed seemed fine but only had it installed maybe 10 minutes.
ADWLauncher (EX) - Do I really need to say much about this one? Good speed, lots of themes, love the dock, nice effects. Most should have heard of this so I won't go into it.
Claystone Launcher - This one is a bit different than most and it's kinda hard to explain why. It's best to look up a video to get it, but it has some nice 3d effects that stack apps and web bookmarks and stuff. Really can't think of how to explain it. Has a few free themes (I think only free if you post on facebook about it?) and the themes aren't really anything special. Speed is a little slow but not too bad. One of their "stacks" has some movies you can watch for free (from youtube) but it's a limited selection and the movies don't look very good to be honest. I'd say check it out just for fun but I personally couldn't use it from day to day.
EZ Launcher - When I tried this one I had some problems when I deleted extra screens and set up my icons. The screen order would change and I think I ended up with a blank screen where I had a couple icons before. Not sure if that's been fixed since then. Speed is a little on the slow side. The have a search function in the app drawer and I love that kind of thing. They also have the option to show all apps in alphabetical order and what they call Genius order. Genius is just basically what you use the most shows up first in the list. They have a few handy widgets you can download for free like task killer widget and weather and sms inbox. Not sure on the themes.
Espier Launcher - This one is made to look like the iPhone. It was pretty slow in my experience, especially when using the spotlight (search on left most screen) feature. You can change the icons around but it shows all the apps you can launch all the time (no app drawer). You can actually choose to hide apps of your choosing but I'm not really a fan of these types of launchers.
Go Launcher - Lots of themes, lots of switching effects, lots to customise. This is a lot like ADWLauncher EX as far as I can see and ADW seems faster to me so I usually stick with that one when using that kind of launcher. Plus I like the bottom dock thing in ADW better as well.
TSF Shell - Very heavy on the 3d and fancyness that's hard to explain. Main desktop is an all your apps desktop, but you can drag icons to other desktops and arrange how you please. You can make folders on the desktops, but there's a limit to how many you can put in one folder. That annoyed me. This launcher is actually really fast. I wouldn't think it to see how it works, but it's actually fast. BIG annoyance is that you can't use a lot of widgets that are big (4x2). Beautiful Weather is a good example. Can't use the clock+weather widget. Annother downside is that it's really expensive for this kind of app at $16.80 U.S. dollars. If it were cheaper and didn't have the widget problem, I could use this on occasion.
MXHome Launcher - Has a fancy 3d clock that's interesting. Was a bit too slow for my tastes but they may improve that in the future. It does have some themes but I didn't look into them. The speed kept me from using it much to see all the features, but look at the video on their page in the Play Store to get an idea of some of the other features.
Regina 3D Launcher - Very fancy...very slow. Didn't use it much but it does look cool.
Hi Launcher - This one by default has a widget area on the top of the screen and apps below in a different area. You can expand the app area to take up the whole screen though. You can categorise the apps in the bottom section for easier access. Speed was okay and I think it was themeable. I didn't care so much for the concept on this one but it wasn't too bad. Worth checking out to see how you like it. Might be hard on the battery but I didn't play with it long enough to see for sure.
Launcher Pro - A lot like Go Launcher and ADWLauncher. Themeable, transision effects, decent speed. This one should be fairly well known so I won't get into it (plus it's been awhile since I had it so I don't remember much ;-P)
Zeam Launcher - Don't remember much about it other than it's fast.
ssLauncher.- I think I saw that one covered here already. I think it was kinda slow but not too bad. I didn't like the concept on how it worked so I didn't use it long.
ICS Launcher - Slow. I played with the ics alpha that is in these forums and I noticed there's a lot missing from the ICS Launcher in the Play Store. Tried it for like 2 minutes then removed due to speed.
Lightning Launcher - I was looking through my installed list on the Play Store and I saw this there. I totally forgot I ever tried it and I don't remember anything about it so there must have been something I didn't care for in it. The reviews on the Play Store say it's fast and it looks like you can rotate your widgets and icons in any direction and stuff. I see it was updated on April 6th though so I might give it another go. [EDIT] I tried this one out and I kinda like it. It's very customizable for sure. You can have the icons snap to a grid so they all line up nice and neat, or you can turn off the grid and put icons wherever you want and in any orientation you want. Want upside down icons? No problem. You can add widgets to if you get the LWW Any Widget (or something like that) plugin. You don't scroll left and right to get to new screens on this one. You basically have one screen but you can build down lower than you can see and just scroll down to see them. There is a pager plugin that will give you (I think) up to five desktops. Anyone familiar with virtual desktops in linux will get how this works. Each desktop can have a different wallpaper and different type of layout. This is a good one to try if you really like to tweak the way your screen looks.
aShell Launcher Homescreen - Has an interesting docking bar that you can drag up to access things like the call log and sms inbox and running apps (that you can kill). By default they have a clock widget on the desktop that looks like it has the weather but when you click on the weather it opens the Play Store and you have to pay $4.95 for it. I thought that was irritating but whatever on that. Had some transition effects and the speed was okay. Don't remember if it had themes.
Home++ Beta - Speed wasn't horrible but not great either. Their dock bar at the bottom is different than most. You scroll left and right on it and it has the date and time down there and you can control things like wifi and sound. It hides the notification bar though and I don't know if that can be changed. I use the notifications more than I realised before installing this. Got rid of it pretty fast.
I think that's about all. I know I didn't give a lot of info for a lot of these, but hopefully I listed some that aren't well know and someone might like. Personally I spend most of my time in either Nemus, Xperia, or ADWLauncher Ex depending on my mood. I do like to experiment though so hopefully I'll see something new here that I can play with :-D
I tried a couple more launchers that I thought I'd share.
Phoenix Launcher - Not free but cheap. Looks like ICS but of course doesn't have all the same features. Faster than ICS Launcher. If you want to try this one read the instructions before launching. Says something about moving it to /system/app or something like that to make one of the more advanced features work.
FTL Launcher - Stands for Faster Than Lightning Launcher. This one is based off the Gingerbread launcher and tweaked for speed. It is very fast. Also not free but not too bad (less than $3). I don't really see much different from the stock Gingerbread launcher than the speed boost. But if you liked stock then take a look. It also says it "- Includes anim speed: precise control over core Android windows/transition animation speed". Didn't play with this but might be interesting.
