Waze is cool, but for my money, no app beats the stock Navigation app that comes with 2.1. I actual prefer it over my Garmin, which I'm not selling on eBay, since I shan't be needing it anymore.
Here are some cool apps I couldn't live without:
Advanced & Automatic Task Killer (FREE) - For automatically and/or manually killing apps running in the background (as if you didn't know that already)
AntiVirus (FREE) - Because who wants viruses or malware? Really.
Google Goggles (FREE) - Amazing app! You take a picture of any object, the app scans the picture, then searches and displays Google results for the image. Works 80% of the time. Has yet to prove it's self useful, but impressive all the same.
Metal Detector (FREE) - Another app that hasn't been of any real use to me, but it absolutely amazing that the phone actually can, and DOES, detect metal!
MyBackup ($4.99) - Has saved my ass at least twice so far. Backup contacts, applications, call log, bookmarks, SMS, MMS, System settings, Android Home, Alarms, Dictionary, Calender and your music playlist.
PdaNet (FREE) - Works flawlessly for tethering your Droid. There's a bunch of these programs out there, I know, but this one is simple and effective.
Scanner Radio (FREE) - Awesome app for listening to local police and fire frequencies. Great app if you're nosey like me!
ShopSavvy (FREE) - Barcode scanner on steroids! Can't think of an option you could ask for of a barcode scanner this app doesn't have. Lists items online by price and locally by price. Create and edit a wishlist or be notified when an item you've scanned becomes available for a price you set. Tons of other cool features.
TV Guide (FREE) - Because the preview channel doesn't come in in my bedroom, so I can just grab mu droid and see what's on. App is based on your local provider and updates automatically!
Where's My Droid? (FREE) - Can't find your Droid? Send a text message with your key word or phrase and it will start ringing, even if you have it set to silent/vibrate! Actually LOST your Droid? Send a text message with your key word or phrase and it will give you it's location via GPS. One of those programs you hope you never need, but are priceless if you do!