RCTGo.com seems to be a good place for everything RCT3. Are there any other sites worth visiting? I haven't come up with anything decent besides this one.

Is there any good repository for RCT2 at all? My Google-Fu has failed me in that regard. All I keep coming up with is randomly scattered scenarios offered on some people's site or older sites whose download sections are all sorts of borked.

It's been so long since I played an RCT game, I can't really remember what sites I used to use. The one you posted is good, though. Still quite active from the looks of it.

I found this page very useful: http://www.lunatim.com/lunaland/3tracks/3tracks.htm

It has 8 track packs totaling over 180 designs, many of which are scenario friendly (low cost, small footprint, good excitement/intensity). I'm on the last scenario of the main game and I think I've used at least one in every scenario.