IR receiver
I decided to build an infrared remote control receiver for my computer, based on these instructions and this page. It would be useful for controlling MythTV.
It connects to an RS-232 serial port, and fits inside the backshell of a DE-9 connector.
I have installed LIRC (hint for Debian users: version 0.7.1 in etch doesn't seem to work, but 0.8.0 in sid works fine). The remote for our Kenwood stereo works very well (even when pointed nowhere near the receiver), the remote from our Mitsubishi VCR works reasonably well, and the remote from our Philips DVD player barely works. I have set it up to control Amarok, and also tried it with MythTV.