site or tool for finding niche sites by popularity?

[dickbaker]

I'm wondering if there's any tool or website that gives you the ability to identify top-ranking or highest traffic site in a particular niche. I'm trying to find sites on which to advertise, and would like to find the best candidates quickly

Is there any such source or tool?

[ACFilterGuy]

One easy way to accomplish this is to go to the google external keyword tool and do a search for a particular keyword you have focused on. Once you look at the number of searches conducted for each keyword, you can then choose those you have identified that are of interest to you. Also, you can use the keyword tool to tell you what keywords are being used to get to top performing sites by entering a specific website into the box adjacent to the keyword box. If you need more clarification, let me know. John Mauldin, www.HeatingandAirFilters.com