One of the more interesting DIY technologies to come out in the last couple of years are the e-Textiles. A very cool combination of electronics and sewing. Using surface mount LEDs, easy to program microcontrollers, and conductive thread, you can make clothes that glow.

The LilyPad is probably the gold standard for this stuff. Arduino compatible, well made, and nicely modular.

The folks over at SparkFun have a complete design kit, if you are interested in getting into it. Check it out here: LilyPad Design Kit