Those of you who were surfing the web a few years ago might remember a website called SixDegrees, circa 1998-2000.
It was an interesting website based on the '6 degrees of Kevin Bacon' idea. You created an account and linked yourself to friends, who were linked to other people and so on and so on. that way you and your friends formed a network with all the other thousands of people signed on as well. Pick any two people, and the website would compute how many 'degrees' away the two of you were. I always thought it was pretty cool. It shut down at the end of 2000, for reasons I've not been able to find out yet.
Recently a friend of mine sent me a link to a similar site, Friendster.com which is based on a similar concept. It's not quite as full-featured or as easy to find people to link to as the old SixDegrees site was, but this one still seems interesting and worth checking out.
People interested in more ways to meet others (for purposes other than dating) with common interests should check out another website with an interesting concept that I ran into a little while ago: Meetup.
The idea behind this one is simple. They have a big long list of things people are interested in. Software, programming, Slashdot, gardening, etc. Go to the Meetup site, register and tell them where you are. Then search the list for things that interest you, and see who else is interested in the same thing in your location. Then once a month, you vote on a location to 'Meetup' (usually restaurants or bars) and if there are enough of you, you all meet at that location and get together to discuss whatever.
A good concept I think, providing a way for people who probably otherwise wouldn't have the opportunity to meet each other in regular life. I've been to a couple of Slashdot meetups in the Charleston area, although haven't been able to make it to much more for other reasons.