These are the resources we're using.

Star Wars Technical Commentaries - Commentaries on the science, technology, and military of the Star Wars universe.
Star Wars Blueprints - Blueprints of ships from Star Wars.
The Blueprints - Image Database - More blueprints for Star Wars.
Starship Modeler Ships Index - Models based on Star Wars craft.
Amazing Starships: Star Wars Reference - Large collection of photos of movie models and other references
Star Wars Design Alliance - Near professional orthographic reference material of various ships.
XWA Upgrade Project - A collection of upgraded craft for X-Wing Alliance. Some of our testing models are borrowed from here.
TFHB Technical Database - Some information on various craft from the Star Wars universe.
The Force.net Encyclopedia - An encyclopedia of information on the Star Wars universe, hosted on theforce.net.
Star Wars: Databank | Starship Archive - Just what it's called, an archive of numerous vessels from Star Wars.
Wookieepedia, the Star Wars Wiki - This is a fan run wiki-style encyclopedia of all things Star Wars. Numerous images of craft.
The Essential Guide to Vehicles and Vessels | On Amazon.com - Cited in the forums as an excellent resource for any Star Wars Modeler.

There's a lot more places to find Star Wars technical data. We surely haven't used all of them, but we are very thankful for the help we have gotten.
If you can think of a site we have forgotten, please post it in the forums.