http://www.olimex.com/ is a manufacturer of microcontroller boards and accessories at very interesting prices. Amazing customer service.

SeedStudio is the maker of a lot of interesting hardware including pocket-size oscilloscopes.
European suppliers:

• hwkitchen has the scope and buspirate
• watterott has the OpenLogic sniffer, the buspirate (from Dangerous Prototypes)

http://sugru.com// sells a silicone-like putty which can be formed by hand, and becomes a flexible rubber in less than 24 hours.
Useful for small repair jobs (cables, keys, etc.)
Extremely cheap (about 12 € for a bag of 12), excellent customer service.

teensy usb is a standalone board which can emulate a serial, mouse, keyboard and other devices while accessing I/O pins.
Available from http://www.pjrc.com/