B & H - My favorite "toy store". From beginners to pros, camera, video, electronics...
Digital PhotographyReview - In-depth camera reviews and forums
sensor-size.com - A website with a digital sensor size calculator. Conversions between ratio and millimeters. Here is a link to David Pogue's original article in the NY Times
Archival Methods - Archival quality page protectors, binders and supplies for storing photos and negatives.