So when I see all these modems for BBC Micros, Spectrums, Commodore 64's etc. etc., they would have been primarily used for BBS, and If I get ahold of one and the right software, I could access a BBS?
Yes and Yes.
Perhaps the easiest way to play around with BBS's, and experience a bit of the nostalgia the rest of us are talking about, is to try a couple of BBS's via telnet. You can access them from any modern PC that has an internet connection and a telnet client. I'm currently a member of three telnet BBS's that I check in with once or twice a week (waaayyyy down from my every day check in's, back in the good old days!). It also saves your phone bill ;-)
Here's a link to a site that lists telnet BBS's:
I'm sure there are others out there, but this is the one I use.