I know I should advance this without having the "goods" at hand, but I am compiling a list of kart tracks, the same way I have been doing (not in the last three months... sigh) for "regular" tracks. When I finish, I will post it here. The list I'm doing includes links to find out how much it costs and when you can learn to "kart" at different kart tracks. BTW, thanks for the clues about "new tracks" (for me, at least) given by several of you.
I strongly recommend (if you haven't seen it already) the tips and tricks you can find at http://www.karting.co.uk/KandK/Tech/. Look in the "General" section. It may help. It helped me (no big deal!) to be the "best" in the "celebrities" karting race at Tocancipá, when we resurfaced the track several years ago, specially when I spent a couple of dollars learning to drive in the wet, following the recommendations given in this site (well, its predecessor).
Tom could take a look at the overtaking section. I only hope he doesn't destroy the kart following that lead!