These guys have been asking me to post their cool new Interface tools for WoW, and I told them I'd put them in front of people - so here you are. It's a pretty neat suite of functions, but the main reason they wanted me to mention it is that their Auction Manager functionality is shit hot, but requires that this client be installed on everybody who wants to use it. I think the best case scenario for them would be complete ubiquity for their package, and since they're plugging what I see as holes in the existing interface it's a noble goal.
If this kind of thing intrigues you, Blizzard has a whole forum dedicated solely to interface mods. Might want to drop in there, maybe see how SoulessDragon in getting on.
(CW)TB