brujula-chess is a free chess app with various skill levels and a fun style of play. It is only 50k large.
Chesley is a chess engine targeting Unix-like platforms and the xboard GUI. It implements a number of modern chess programming techniques, including bitboard move generation, transposition tables, etc.
A secure Linux system with Grsecurity and many penetration tools.
A control protocol for various astronomical instruments (telescopes, CCDs, etc).