Free Universal Instant Messaging for Windows Mobile Devices

http://www.movsoftware.com/products/imov/imov.htm

Communicate with Google Talk™, AOL™, ICQ™, MSN™, Yahoo! Messenger™ and Jabber™ users!
Easy setup and use
Wireless capable
Encrypted communications (SSL) support
Support for most Windows CE devices-including the PocketPC and Microsoft Windows Powered Smartphones!
Automatic new version notifications
Offline message queuing
SOCKS5 proxy server support
Seamless offline/online operation
Location Based Services support