The series in chronological order:
Mobile Suit Gundam
Gundam 0079: 08th MS Team
Gundam 0080: War In The Pocket
Gundam 0083: Stardust Memories
Gundam 0087: Zeta
Gundam 0088: Double Zeta
Gundam 0093: Char's Counterattack
Gundam 0123: Formula 91
Gundam 0153: V Gundam
And the alternate-universe series:
Mobile Fighter Gundam G
New Mobile War Chronicle Gundam Wing
After War: Gundam X
Turn A Gundam NEW!
Gundam is currently being released through AnimeVillage.com. Only the Gundam Movies 1, 2 & 3, Stardust Memories and War in the Pocket have been released so far; depending on sales, the rest of the series will follow. Gundam Wing is now playing on the Cartoon Channel in the US and on YTV in Canada; check EX Magazine for more info.
The Gundam Project your one stop Gundam shop
The Mecha Domain all the specs for every mech in every series, yeehaw!
Gundam Silhouette a conversion of the Silhouette RPG system (Heavy Gear, Jovian Chronicles) for Gundam. very cool.
FTP Archive of Gundam Pics pretty self explanatory.