This is an old post, preserved for reference.
The products and services mentioned within are no longer available.
I've bought one of these recently, and it's great.
USBtiny ISP from Adafrruit.
6x1 programming clip.
DSTIKE's Tindie store.
Update:Disaster. The plastic on the bottom of the clip has shattered.
2022 Update: I have still use these, but have removed the lower section all together and just hold it in place.