Does anyone knows a site where you can buy great tabletop games

Question

Like dungeon and dragons.

There might be a little rpg in it.

Answer 1

Depends a lot on what you're looking for.  Some good sites:

http://www.paizo.com  good general site, nice mix of boardgames, rpgs and the like, some downloads.

http://rpg.drivethrustuff.com/  a very good site, especially for downloading that out of print rpg you just have to have.  A lot of stuff here that's significantly cheaper than hardcopy.

http://www.trollandtoad.com/  a nice site for card games like magic and minatures games, also has a good selection of boardgames and rpgs.

http://www.funagain.com/control/main  probably the best commercial boardgame site I've seen

Answer 2

the "marketplace" on boardgamegeek.com

Answer 3

Try paizo.com. They sell different editions of D&D as download files. You could probably acquire an entire library of a previous edition for the price of a 4th edition book.