I bookmarked this quite some time ago and just today got around to playing around with it. Although you'd certainly want to do more in-depth research for any purchases, it's a really nice tool to get you pointed in the right direction if you're looking at buying a Canon body or a new lens or flash for your current Canon. Unfortunately, it only has info on Canon equipment, so you can't compare a Canon to a Sigma or anything like that. Also, if you were ever wondering something like what those makes those L lenses everyone talks about so special or what all those numbers are printed on the side of your lens, it provides some easy to read explanations of all that as well.
http://photonotes.org/lookup/
http://photonotes.org/lookup/
