siren similar

Cloud storage and file syncing service, similar to Dropbox; free 15GB account.

Tiling window manager similar to xmonad.

Drawing app, capabilities similar to Illustrator/Freehand/CorelDraw.

Rapid engineering and scientific prototyping, similar to MATLAB.

Kakuro is a Japanese number game similar to Sudoku.

An easy-to-use calculator for Points similar to "Weight Watchers Points".