Don McGregor's Cyberpad
Mr. McGregor wrote, along with P. Craig Russell, the brilliant post-apocalyptic Marvel comic "Killraven". Find it, read it, love it. He also wrote "Sabre", which is widely considered the first true graphic novel.
The Grand Comic Book Database
Another database site, but this one has great scans of comic covers. Rarely lets me down when I'm looking for a graphic.
Wiki site dedicated to Kurt Busiek's "Astro City". If you love super-hero comics, and you're not reading "Astro City", get out there now and buy the first trade. I guarantee you won't regret it.
And from my collection of check lists, because I'm ridiculously anal retentive....
Generation X Checklist
Gen X was an excellent comic. Should you be a fan, this is a pretty complete list of all their appearances.