A list of BBS's that I personally try to call and support on a regular basis.
I have been maintaining this BBS List specifically for Atari (real or emulated, A8 or ST) BBS Systems that the community can assist with maintaining.
A Vintage BBS list maintained by my friend Justin Scott. He does a great job of maintaining this list and you should really consider using it as your starting point if you're in to Vintage BBSing. While you're at it, check out his BBS "DJ's Place" (it's in the list).