The Dave Haynie Archives, where he has collected old Commodore documentation on various kinds of Amiga hardware.
Gprof2Dot, is a tool that produces call graph profiles based on data from a plethora of profiling tools.
A Bit of Physics Humour, or how to measure the height of a tall building by using a barometer.
Linux Compose Key, learn how to effectively write characters that aren’t available on most standard keyboards.
SCIgen – An Automatic CS Paper Generator, generate computer science papers on-the-fly. Would be cooler if you could actually control the subject, nevertheless it’s still an interesting concept.
The V4Z80P, a Z80 laptop. Mucho geeky!
google-perftools, provides profiling tools for multi-threaded C++ applications.