I have used capterra.com but it can get pretty expensive because it is an auction kind of setup. Highest bidder gets listed at the top. The company was recently acquired by gartner. They also have s free listing option. Depending on how crowded your specialty is, your results may vary.
I also use a software spyfu.com to research competitors keywords and seo effectiveness as well as what they are likely spending on Adwords. I use several other tools that help me get more done.