I just stumbled across an old mini-project that I was working on a while ago--adding UCI support to an open source chess engine called cheops:
http://www.nothingisreal.com/cheops/
You can download the UCI version here:
http://web.mit.edu/myee/www/chess/cheops-1.1uci.zip
The executable is in the bin subdirectory (along with the required cygwin1.dll file). To start it in UCI mode, you need to use the command:
cheops --uci
It seems to work fine under arena (on a windows XP system).
Some comments/warnings:
- has no time control
- takes a long time to search, so set the search depth UCI parameter pretty low (maybe 3 or 4?)
- not too strong (maybe around pyotr amateur level?)
- still could be fun for beginning humans to play
- has a lot of static eval parameters to tweak
- likes to get its queen out early
Michael