One of the best ways to grow an audience is to find other audiences in your industry. Similar Site Search (Similar-Site.com) does just that, and more. Simply enter a website into the search bar at the top and you'll get a list of similar websites as results. Furthermore, you can click the "tool" button at top right and adjust settings - such as search depth, tags (deselect tags you don't want to include) and the ability to add tags to your search.
Websites are a good start. But you can also narrow your similar search to specific URLs. So, if you find an article interesting, copy the specific URL into the Similar Site Search search bar and you will get similar results based on that specific URL's content. Should a search turn up empty or with lackluster results, users are prompted to add tags to refine the search and help future searchers.
We have experimented with the tool and so far the results are very positive. For publishers this is an excellent way to find targets for new audiences, places to leave blog comments, resources for new links and to keep an eye on the competition. For advertisers, Similar Site Search is a nice (no-cost) way to find potential channels to advertise with or future partners. Another thing we like - no registration is required.
Similar Site is relatively new and they are working to make the service better and more in-depth. But this is definitely one to keep bookmarked - there is always tremendous value in researching what's happening in your industry.