Rule of Cool’s Legend, a d20 System released under the Open Game License.
Rule of Cool’s Legend is a d20 System designed by a group of enthusiasts who wanted a system that was fast, fluid, and elegant, and which was both flexible and robust. All proceeds from the Core rulebook are donated to the Child’s Play charity.
The system is class-based and level-based. Each class consists of three “tracks,” each of which contains seven “circles.” A character gains one circle per level (except at 1st where he or she gets two), cycling through the three tracks until all 21 circles have been obtained at 20th level. A character can multi-class by trading one track for a track from another class.
Compared to other d20 Systems, most notably Dungeons & Dragons 3.5, Legend is more gamist and abstracts more details in the interests of fast and fluid play; simulation is a decidedly secondary priority.