The PSXSDK is a free and open source software development kit that enables anyone with C programming knowledge to make programs and games for Sony's PlayStation console. Everything was either written from scratch or based on already available open source resources. It is thus free from any proprietary code and fully legal to use. The SDK is mostly geared towards a *nix environment, but is fully usable with emulation environments such as MSYS and Cygwin.
WordBash is a Wordpress clone written in Bash, the GNU Bourne-Again SHell. Everything is generated and output by Bash. No AWK. No SED. No TR. It is all Bash (with one exception). It is a CGI script with an attempt at an OO-like design. It currently supports posts (categories, tags), comments (with spam rejection), themes (true templates), and code highlighting as an administration addon. The current script size is 21 files of about 2500 lines and only 44 kilobytes.
RufasCube is a slider puzzle where there is a 3x3x3 arrangement of cubelets with the center one missing, allows sliding permutations. After a randomization, the goal is to restore the cube to its original configuration based on color and alphabetic hints. It is challenging, but not as difficult as a Rubik's cube. Here, diligence pays off. Also, incremental solution is possible - you can unscramble one slice at a time. When you finish, you can see the entire English alphabet appear on the 26 cubelets. It supports laptops and Mac Retina displays.