Welcome to the dark side.
I've had an HTC Magic (aka MyTouch) for about a year. Here are some of my favs:
-SugarSync: This allows you to set a folder on your PC and one on your phone and have the sync automatically. So any file you stick in the sync folder on your PC will be available on your phone. I have a voice recorder app on the phone and I set the folder it records to to sync with my PC, and now I have all my voice notes available on my computer.
-KeyPass: Good, free, secure app for keeping track of passwords. Again, I sync the KeyPass file so any new passwords I put in are available anywhere.
-Google Goggles: Hard to describe. Get it and play with it.
-Google Listen: podcasts...just install everything made by Google.
-Layar: augmented reality. Very sci-fi.
-Color Note: Write postit notes and stick them to your home screen.
-Google Sky Map: Many dimensions of awesome.
-PicSay: Photo editing.
-SeePu: Geeky. See memory usage and CPU cycles.
-Space Physics (game) not really about space or physics, but great puzzles. If you like it, the other games made by this company are also great.
-Advanced Task Manager: You should have some kind of task killer. But there is a tendency to want to kill tasks when your phone slows down. This is actually not a good idea
. But you'll still need one for emergencies.
-Astro: for file browsing, management.
-Tasker: I saved this one for last (I hope you are still with me). Whatever reason you told yourself, this app is actually why you got an Android phone. It enables you to program all kinds of cool things
. I've only been playing with it a few days, but I'm blown away.
These also have good forums for when you have questions.
Android apps on Gizmodo
That should do you guys for now. I'm envious. The Magic was the only Android phone available in Japan when I got it, and they haven't updated it beyond version 1.6. Also, most of the cool things you can do with maps and location stuff is better in the US. Still, I love my phone.