Japanese Official Sites (Ryuusei 1)
XEBEC
TV Tokyo
ShoPro
Capcom

Japanese Official Sites (Ryuusei 2/Tribe)
XEBEC
TV Tokyo
ShoPro
Capcom

English Official Sites
Toonami Jetstream (Where the dub episodes were aired)

English Blogs
Nigoli
ToadMan.EXE
Protodude
Mui Mui's Place

English Fan Sites
The UnderSquare
Rockman.EXE Online
When Stars Align
On Air
Rockman Metropolis
The MegaMan Network

Other Sites
Wikipedia Article
Ryuusei C2 Community @ Fanfiction.net