Hi,
I quickly wrote an AAC Winamp3 plugin. It works with Winamp3 beta 1, which still seems to be extremely buggy. So let's hope for newer beta versions soon :-)
The code is in CVS and all it does currently is play a file, no seeking or info whatsoever yet. So if you want you can try it out.
www.audiocoding.com
Have fun,
Menno