CMake - CMake is an open-source, cross-platform family of tools designed to build, test and package software.
Creddon - Tweet for a cause and a sponsor will donate $1 to charity
SCons - SCons is an Open Source software construction tool—that is, a next-generation build tool.
Send Mail Get Mail - A postcard-sending website.
Ninja Build - Ninja is a small build system with a focus on speed.
Postacard - Text a photo to send it as a postcard for $3.