Pocketwit

Pocketwit is a free open-source Twitter client for Windows Mobile devices (PocketPCs and SmartPhones.) with number of functions. The application is open-source under MIT license and built with .NET 2.0 compact platform.

The application has number of notable features like updating your location (requires GPS), grouping your friends, multiple accounts supporting, sharing images using different photo sharing services (TwitPix, Yfrog…), taking and uploading a photo from your mobile camera, and long tweeting using shorttext.com. It supports identi.ca accounts as well.