Looks like AOL is actually after 10.1 billion years is finally working on a modern free AIM client for Windows Mobile 6.
http://beta.aol.com/projects.php?project=aimwinmobile
What is AIM for Windows Mobile?
AIM for Windows Mobile brings all of the best features of AIM on your PC to your Windows Mobile smartphone! AIM for Windows Mobile lets you communicate whenever you want, wherever you are, in whatever way suits you best - IM or text. Update your AIM status and information when you're on the go. Change your conversation style, manage your Buddy List, and much more. AIM Windows Mobile Smartphone has many of the same key features and a familiar look-and-feel of the desktop AIM client.
Please note: This build of AIM Mobile does not have an Update Mechanism available. This means you will have to return to beta.aol.com and check if a new build of AIM for Windows Mobile is available. The Update Mechanism will be included in a future build.
Supported Devices: AIM for Windows Mobile is supported by ALL Windows Mobile 5 and Windows Mobile 6 devices. Some examples are:
* T-Mobile Wing
* Sprint Mogul and HTC Touch
* AT&T Blackjack II, Tilt
* Sprint Samsung ACE
* Motorola Q
* Verizon Wireless 6800
* Most Palm Treo's
*U.S. only. AOL Mobile services may require a wireless data plan and charges from your wireless carrier may apply. Not all AOL Mobile services are available on all wireless carriers or on all wireless devices. Check with your wireless carrier to confirm that product use is consistent with your carrier's Terms of Service.