I'm pretty sure Fire would let you do that ... it lets me run multiple accounts from seperate systems, I've never tried two AOL accounts on it. It may not work, though, if AOL uses an IP addressing system. You can find Fire on versiontracker.
when i used fire, it couldn't be connected with 2 aol accounts on the same time, or with an aol and a .mac account. but it was months ago, and it can have improved already.
proteus could and still can though.