Google Voice -Completely integrated into your Droid NICE!
Locale - This looks like a better option to sound profile control than Timeriffic. It sets itself by your GPS location. Still haven’t set it up yet.
Meebo - The all in one web based chat client for those friends who just won’t go Google.
KeyRings? - Sick of those plastic reward cards on your keyring? Load them into Droid and help your keyring slim down ;)

Currently MIA in the Market but ShopSavvy? seems to do the same thing? Weird this was on the PCWorld must have list and now it’s vanished.

Compare Everywhere - Use this to scan the barcode on any item in the store to pull up reviews and price comparisons. I FREAKING LOVE THIS!!! I don’t make a big purchase without checking reviews and prices first.