Quick facts
Completely free and Open Source (including firmware)
Programs PIC10-12-16-18, 24xxxx I2C EEPROMs, 93SX6 MicroWire EEPROMs, some ATMEL micros, communicates with generic I2C & SPI devices (see supported devices)
USB 2.0 Full Speed interface, HID class (same as keyboards, mice, etc.)
Self powered
Doesn't need drivers
Built from easy to find components (estimated cost ~10€)
Hardware generated timings for maximum speed and reliability (writes a 18F2550 in 15s, 8s under Linux)
Doesn't saturate your CPU and doesn't suffer when other programs are running
Open source control programs for Linux and Windows
http://openprog.altervista.org/OP_eng.html#Download