It also depends on which version of D&D you want to play. Some people, like those I game with, play Pathfinder and call it "D&D." We feel it's a closer spiritual successor to the name than 4.x. Other people feel differently. Some are still playing 3.5, 3.0, Advanced Dungeons and Dragons 2nd Edition, or even the old Red Box. It really depends on what you're looking for, what your local groups are, and what you're interested in doing.
If you're interested in playing something that isn't currently being released and still is like D&D, you can view
the 3.5 SRD or
the Pathfinder SRD, where you'll find most (the 3.5 one) or all (the Pathfinder one) character creation rules and system mechanics. That's one of the nice things about the d20 system games - the mechanics are available for free, rather than through a compulsory subscription service. If you like Pathfinder enough, you can even get the Core Book in .pdf format for only $10, and it'll be very pretty.