Hrm, I can't check into this right now (proxy blocked sites and they'd throw a fit if they caught me unblocking them for my own amusement) but I'd recommend reading up on trillian. Go to www.trillian.cc and read over the site.
I have not used it myself, but I know it integrates itself for use with any of the major IM programs out there (ICQ, Yahoo, AIM, MSN (I believe at least).
You'll need to check up on the FAQ's and system side of it to see if it connects up to any of the login servers you're looking to avoid.
The last option I'd have to say for you, is to look into finding a freeware version of a system connection software, several of these come with built in chat programs, perhaps one could be utilized to work within the parameters you're setting.
Another option is Hyena, although only you can send messages and cannot receive any kind of feedback through it.