Feel free to e-mail me if you want to be linked to or have a suggestion for a link.
The Gundam Project used to be the best online source for Gundam info. Now it is unfortunately shut down, but it is still on the links page because the image gallery is still up and running. Check it out.
Gundam.com is home to a great model and fan art gallery, and one of the best fan-created Gundam sites out there.
MAHQ has extensive drawings/scans on just about all of the mobile weapons in the Gundam Universe, along with anime reviews, editorials, and too much more to fit into this paragraph.
Newtype Asylum is the Gundam fanworks site. Model reviews, mecha profiles, and anime reviews galore. Check it out. Now.
Mobile Suit Gundam: High Frontier has just about all the info on space colonies you'd ever imagine.
Gundam Shop is a great Gundam online store and fanart gallery. One of my favorite places to buy models.
Hobby Link Japan Another great online store with extremely low prices. I would buy my models from thre, but I'm far too lazy to wait for them to arrive from Japan.
Image Anime is one of the best online anime stores out there. The other place I buy my models from.
Gundam Official is the official U.S. Gundam page.