That's a pretty cool map info site AcE :)   
  
I've just been checking it out, learned a couple of new things, and will be back when i'm trying to incorporate some of it in to my trickjump map which is half-built. 
  
There are quite a few good mapping websites, but it seems you get some gems of good info from each one rather than there being one complete source. 
  
modsonline is definately a good mapping info site, so with that already mentioned, and in no particular order, I like:  
  
  
Surface 
map-center 
Splash Damage 
Tram Design 
Jolt Mapping forums (no longer a fully active mapping forum but some good info still in there) 
Map-Craft - nice helpful ppl and some very good tutorials which are helping me get my map in to shape 
  
Good luck with it. :)