I founded out about Tasker just a few days ago, and for me, its almost the best app in the market.
Only your mind sets the limit, tasker can do pretty much everything.
Here are my profiles so far:
Turn on GPS for Maps, Mytracks an MyPlaces, and turn it off when app is closed.
Sleep - between 23.00 - 05.00, notify me its time to sleep, turn off wifi, and silent mode on.
Wired/Bluetooth headset connected - ask me if i want to start Mediascape or Spotify.
I always have Wifi on, except during sleep time.
So "Wifi Home Connected" connects automatically to my home network, i get a permanent "connected" notification in the bar, vibrates, turns off the keyguard pattern, set ringer and mediavolume, and shows a popup with a background-image of my livingroom, welcoming me home.
When i disconnect or get out of range, the keyguard pattern turns on, removes the "connected" notification, vibrates, change ringer and mediavolume, and shows a popup with an image stating time to go.
A widget-task that shows all currently active profiles in a text-popup, when tapped.
When i recieve a sms or mms from someone in my family, i have a voice saying
"You've just recieved a new message from your mother/father/sister". and "...from a favorite contact" when i get a message from a person in starred contacts.
Right now im working on delaying Wifi to on at boot time, until the screen is unlocked.
Have a few other ideas as well