Are you looking to be playing D&D 4th edition or one of the older versions? Lots of sites facilitate play-by-post or matchups for other types of games. Skype is great and there are a lot of other programs out there which help a lot(maptools, virtual table top, ect). I am also seeing a lot of games starting up using google wave.
Most sites that have something to do with tabletop gaming will have a 'looking for group' type section to their forums and without knowing your preferred edition/system its hard to point you to the best spot for you. Instead I'll give you some possibilities to get started:
Enworld has a huge community and covers a lot of game systems. Biggest setback is that there are also a number of edition flamewars that run through there sometimes.
giantitp.com is pretty good for table-topping too. You make a webcomic that appeals to gamers and thats what you are going to get I suppose, check out their forums for some good gaming with regular games opening up.
gleemax is wizard's official forum site and thus is the place you'll find the most 4th ed games.
Paizo.com is my venue of choice simply because the community is really friendly and great. Because Paizo is the publisher of Pathfinder(A new edition that hung closer to the 3.5 roots than 4th edition) that is the easiest set of gamers to find there, however there is a fair share of 4th ed players as well as those who make use of other systems. WoD gets some good playtime as does systems like Paranoia, iron kingdoms, most of the 3.5 offshoot systems and even some early D&D editions.
Hope some of that helps and good luck finding a game.
just none that play D&D
