I used to run a BBS on my A600... no CPU expansion just an extra 1meg of chip ram and a harddrive...
Used to use MAXsBBS which always ran fine and dandy for me.... can get it on aminet...
later upgraded to use MAXsPro which was just an upgrade for it which added some nice extra features and stuff... was written by a bloke i used to know actually.....
used to write some "doors" for it too.... was a nice little program that...
shame the internet killed off the BBS scene... i still got my amiga HD with the BBS still set up on it... :-D