http://laire.dy.fi/jarcs/
It's a collection of partial solvers, at the moment there's Petrus S1, 2x2x3 block, Cross, and XCross. Some solvers that I plan to add: Roux S1, Roux S2 (using <U,R,M>), MU, Petrus S4, and maybe Kociemba's algorithm for the whole cube.
[edit 20090322]
I rewrote the...