Find Top Sites in Any Category with Weblisty
If you want to know who the leader is in any given category, try a search on Weblisty. This site aggregates data from Alexa and Quantcast to list the sites with the most traffic for a category of your choosing. The site also provides a bookmark so you can find similar sites to any that you find.
A quick test shows that the results seem pretty accurate, although refining keywords may be necessary to get specific. And some categories don't return the best results. So, it's better suited to broad keyword searches. That said, it's a pretty good way to find some industry leaders and perhaps some link bait targets. Find the leaders, do some research and see if you can get included in their indices or even if you can drop a link to your site along the way.