Get TiKL push-to-talk. If you know anyone else with an Android phone, you can talk to them like Nextel. It even works with almost no lag across networks. I was talking to my friend on AT&T and it worked great.
Zedge is good for finding wallpapers and ringtones easily.
The Mario live wallpaper is awesome: Mario live wallpaper for Android: better than a Tanooki Suit in the summer -- Engadget
Task Panel - Great for managing which apps close automatically when you lock your phone, so that you don't have a ton of stuff running at the same time constantly. Saves battery life for me.
WootWatcher - Because it's Woot on your phone
The Amazon and Ebay apps come in handy
The Weather Channel app is good too
My Verizon - Quick and easy way to check on your usage
Meebo IM for all your IM needs
Barcode scanner - For things like scanning barcodes on websites that'll take you right to the app they're reviewing etc...
Bump - Allows you to share apps, pics, sounds etc by bumping phones together, even if the other person has an iPhone
That's all the app suggestions I have for now.