Since the Motorola Droid only debuted less than two months ago, this list may be a bit premature.  That being said, moving to the Android 2.0 platform and the Motorola Droid has alleviated any iPhone envy I once had.  There may not be as many apps for Android devices as there are for iPhone users, but there are enough to make me a satisfied Droid user.  Here are some of the apps that I have found myself using every day. 

Twitdroid Pro - This is the first app I actually purchased and it was totally worth it.  The Pro edition of Twitdroid allows for multiple Twitter accounts.  Twitdroid makes it easy to add photos and videos to your tweets as well as simple retweeting, DM's and everything else you would expect from a Twitter App.  Twitdroid Pro could be the killer Android twitter app if geo tagging is added in future releases.