I have posted some simple scripts to manage Lists at: http://www.ist.rit.edu/~jxs/tools/scripting/twitterLists.html - I try to encourage my students to get into scripting & to have fun with curl/ grep/sed/etc...
I have noticed a fair amount of chatter around the Web about converting userName to userID, and there is quick-hack code at the bottom of that page of examples (as part of the "addmember" and "rmmember" scripts). If it is useful, feel free to use it (all my stuff is CC licensed). If you have improvements to suggest, that would be great (and with your permission I will gladly fold it into my example scripts & of course give attribution). jeffs aka @jeffsonstein