Free Android Apps

Seesmic, the application specific twitter user, you can update the latest tweets and create the latest tweets through this application. 

Download Here:
https://market.android.com/details?id=com.seesmic

Foursquare, a kind of map to show the location, as well as google map

Download Here:
https://market.android.com/details?id=com.joelapenna.foursquared

Tweetdeck, another application for twitter users and one of the most widely used.

Download Here:
https://market.android.com/details?id=com.thedeck.android.app

Androidify, create an avatar with a shape similar to the android mascot, just use this one application.

Download Here:
https://market.android.com/details?id=com.google.android.apps.androidify