Thanks ... is this really the only way, though? I'd rather not buy any more stuff than I have to. I also really like the Arduino IDE and don't want to start with another program.
I would try to de-solder the USB socket, and break it out on a wire to its own PCB, but my soldering iron isn't powerful enough to de-solder the tags, heh.
How do xBee / bluetooth devices manage to reprogram Arduinos wirelessly? Do thy plug into the ICSP? If they just have access to RX and TX, surely I can reprogram my Arduino with a wired connection in a similar fashion?
Other ideas: the Arduino Pro and Pro mini from sparkfun program via 6-pin header cables (I've got one) ... what pins do they link to? Can I use this cable to program the Mega, with the appropriate connections?
You can use the Arduino IDE to write your programs and simply run avrdude from a command line to program the board using the usbtinyisp connection. The thing is so cheap that you'd be money ahead just ponying up for it and skip the hours you'll waste trying to desolder or build a serial interface and configure it to the Arduino. I can't help you with any of those other options.
Jim.
Actually with a minimal amount of effort you can modify the Arduino preferences file and use the programmer directly from the IDE so say this: