Where do I find information regarding the various levels of camras?

Canon has Power shot, G, D, and other levels
Nikon has the L, P, etc

Where can I go to find what these designations are as to quality?

Added (1). make that 'cameras?'

Added (2). Thanks AWBoater. Now if someone has same info for Canon it would help.

Snapsort.com is quite good for comparing specs, you can also use Flickr's Camera Finder feature to find photos from a specific model of camera.

I would go to the maker's sites.

Years ago my nephew told me about this site. I've see every camera I've owned on it which is amazing since I just by low end cameras. Anyway this may be what you are looking for:
http://www.dpreview.com/...eview.com/