I'm a photography guy. I love it. I'm still what would be considered an amateur at best , but I'm continually studying and practicing to hone my skill.
Anyhow, I just found a new site called LensHero. It's a site that allows you to compare any lenses you like or you can ask it for suggestions based on your needs.
I just did a search on lenses for my Canon T1i for "Low light situations" and it gave me a report on several lenses from Canon and Sigma in the 20 - 80mm range (all prime lenses) and on Tamaron 60mm lens. It provides a very slick look at some vital stats to let you compare across the range.
It looks terrific as a research tool, but I'd really like to see a little more in two specific areas. First there should be some way of showing recommendations or some kind of rating system. For example, they have both a Canon and a Sigma 50mm lens. The Sigma is more expensive, and I'd like to know if it's worth the extra cost.
Second, I think they're missing a few things that would be nice to know from a lens buying perspective such as: number of elements to the lens (affecting the complexity of the lens) and the number of blades used for the aperture (affecting the bokeh).
But, those two quibbles aside, I think it's a great starting point for your lens purchasing research.
LensHero | DSLR Lenses