PockeTwit is a twitter client for the Windows Mobile Professional platform.

Features:

A unique user interface
Works on VGA, QVGA and SmartPhone devices
Support for multiple twitter and identi.ca accounts
Maps view shows users on a world map and allows searching by region
“Conversation View” shows a what this status was in reply to.
Uses standard notifications to alert you of new friends statuses or replies
URL shortening with is.gd
Integration with shorttext.com for tweets longer than 140 characters
Take photos and send to TwitPic
Integrated search.twitter.com
Clickable @names, URLs, and #Hashtags
Option to check for new version on startup
Themes

http://code.google.com/p/pocketwit/