I designed some KeyFobs for my company that had to go be sent out to all of the locations in the field and thought others might be interested in a low cost alternative. It supports both the current Stk500 protocol and a custom protocol through FTDI USB. The Keyfob ability is via a plugin 8M flash module. It also has both 6 & 10 pin standard Atmel ISP connectors, with real voltage level translator/buffers for 1.8V - 5.5V operation.
Programmer without Flash module would go for about $15.00 and about $9.00 for a flash module.