Off late, I had been researching a lot to upgrade my camera to DSLR. I came across many interesting links to help better understand the DSLR and Lenses. Since one needs to know what those numbers are on the lenses and what the DSLR is equipped with before
investing on buying them.
Credits to Nikon to have such learning materials for people to know their lenses.
Lens Simulator - Best place to try out the lens before you buy.
Lens positioning map - Compare focal range & f-number of the lenses.
Terms - All the jargons explained.
Camera labs - Nice video reviews on body and lens. (When tired on reading, listen to the video and relax)
Lens review - user reviews
Photozone - Show me the numbers style.
P.S. Will soon publish my learnings. If you got more links, let me know will update it.