http://www.cars101.com/
Cars101.com is a great site specific to Subarus. The site has great information regarding the specs and options of all old and new subarus. If you are thinking about not using the recommended 02-07 wrx donor, you will want to have this around to learn a little more about the other options that are out there. The site basically brakes down each subaru model by generation and and also describes the differences between differant models and changes that occurred every year of production. it will tell you what engine is in every subaru heck it will even tell you what models have what kind of brakes, which is good to know since brakes can change substantially from model to model even if they were both the same body style and both made in the same year.
anyway, check it out, I'm sure many will be impressed by the information it has to offer, and I'm sure many of the subaru guys already know about this site. Example of what you can find on there. http://www.cars101.com/impreza_archive97_98.html
Impreza specific page
http://www.cars101.com/impreza.html
Legacy specific page
http://www.cars101.com/legacy.html
Forester specific page
http://www.cars101.com/forester.html
Outback specific page
http://www.cars101.com/outback.html