I may have mentioned Pathfinder before, but I thought I'd do so again since the Beta version has been released for download.
Basically what Pathfinder is, is an attempt by Paizo and associated game designers who were disgruntled by 4th edition to create a new version of the D&D d20 system. The idea is to iron out some of the flaws of 3rd and 3.5 ed. while allowing people to easily convert characters/campaigns to it.
I personally think it looks awesome, and the Beta version of the game (the release date is for next year) is available as a free pdf download
here.
So check it out! And if you have any ideas/improvements post them on to the forum.