While not the most elegant looking generator i was extremely impressed with its performance.
A downloadable Generator for Windows
Generate simple islands and walk around them
MOUSE to orbit around, ESCAPE to release the cursor;
In first person mode: WASD/MOUSE to move;
Generating interface on screen
Five topmost sliders control landmass noise parameters (hints on hover)
Generator keeps crashing? Try checking the "Single threaded generation" checkbox (might freeze the game for a few seconds)