See: What are some good online tools for finding compatible lenses?. If left open, this should probably be a community wiki: it lends itself to the "objective list of resources" kind of answering that CW works best for.
There's some debate, I think, on whether those sort of lists add value at Stack Exchange overall; I'm not going to take a position on that. The question is: should that Q be left as it is, or should it be merged with Where can I find reviews of lenses?, and that question edited to include non-review lens-sorter sites, which are already listed in the answers?