Not one but two Digimon wikis. The first leans toward the dubs, the other toward the Japanese originals. They're both excellant:
Shining Evolution
These two sites are favorites of mine, with a the best Digidexes on the net. They also have a jointly run message board of their own which I consider my personal favorite. So if you see a guy called Veedramon there, yeah, it's that Veedramon.
Great site for the card games
Chris McFeely's site, pretty much the definitive source of information about the dubs.
They get all the stuff from Japan first. Several notable subsites, including DMA, another great Digidex, and the new home of File Island, the definitive site on the Japanese virtual pets and Digivices.
Run by Vande, good information on Japanese cards and scanlations of the V-Tamer manga (I mean, c'mon, Tai and Veedramon...how can I not like that?)
The Happy Galgomon Gif Factory
Fenrir's site, with lots of great artwork.