OK, I got the latest Ucontrol but it only seems to deal with remapping modifier keys. They point to this page for general remapping purposes. But not being a coder I really can't get anything useful out of it.
http://developer.apple.com/technotes/tn2002/tn2056.html
Basically I do a lot of architectural numeric input; in OS9 with Resedit I remapped the clear, equal, and * keys to feet, inches, and comma, so I could input xyz coordinates quickly with one hand. Need to set up the same thing in X.