Excellent tool for testing cables. Although primarily targeted for network TP cables, it can test almost any cable or wiring installation. Complete schematics and firmware source code.
Very useful software for reading and writing 93Cxx, 24Cxx, and 24Wxx series EEPROMs. Needs only a very simple hardware, connects to parallel or serial port.
RD2 Kit is a simple and cheap development Kit for quick development of new applications and learning the C language. The Kit contains a T89c51RD2 microcontroller and basic peripherals.