http://www.siemensjobcam.com/mobile-6-1-messenger/
APPLICATION Yahoo Messenger / Windows Mobile 6.1?
I want a full implementation of Yahoo Messenger to a mobile phone that runs Windows Mobile 6.1! I had it for one more phone running WM 6, but there is nothing for WM 6.1, only browser-based and that's lame. I installed a version Full of AIM on the phone but I want to YAHOO!
Try Agile Messenger With http://www.agilemobile.com/'ve tried and it works very well with my Pocket PC to runs on Windows Mobile 6.1
Samsung Code – Howto Install AIM (AOL Instant Messenger)