I recommended it over paying some dude to do it for him. Just thought I'd lend an opinion. My qualifications/knowledge didn't factor in, though maybe they should have. 😉
OP, do it in PHP or ASP, don't get hung up on open source if you happen to be better with one over the other.
PHP, ASP, JSP, Python... you could do it in practically any language. Suggesting ASP and mentioning Access just seems to go against the grain of the typical LAMP platform that small sites (like the OP described) favor.
Judging by the original post, I'd say Brendon doesn't know any programming language with which he could create the site he described. (Sorry if I'm wrong, just making an assumption here.) As such, this discussing seems unnecessary.
Anyway:
Yes, any web developer could pull this off with relative ease. Custom features demand a premium, but hiring a developer is probably the easiest way to get what you're looking for.
Most forum software and such do offer extensive user directory systems, so that's one way to go. It's probably a roundabout way to do it, but if you are looking to host discussions or whatnot, that's definitely a possibility.
Facebook as someone mentioned is another possibility. That's probably the quickest route to take, but then again, it's facebook.