Simple 4-CH 4MHz logic analyzer.
Here’s the project page: ikalogic.com/scanalogic_home.php
The hardware is dead simple. This could be built with an SMD ATmega168 + FTDI chip + mini USB socket into a very tiny package. Would be a good pal for the oscilloscope kit.
Watching serial data/I²C/SPI would be very nice. Also having a software that runs on linux (maybe perl + GTK) would be great. Currently the author offers the firmware + windoze GUI.