Basis of a number of D20 games, some of which resemble D&D3.x closely while others only use the basic resolution mechanic. D&D4 (4th Edition, Essentials) Big emphasis on tactical choice: the game is designed around grid-based combat with lots of abilities that don't just deal damage but move enemies around, apply conditions, &c. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.