SimilarPages is very good for finding new content. Simply enter a URL you know and it finds related pages.
It indexes over 50 million websites and allows you to branch out further based on new sites found.
The SimilarPages Add-On is the free Web Discovery and Search Tool by SimilarPages. For any page you land on, SimilarPages add-on automatically generates a list of similar websites. All you have to do is to follow the links you are interested in.
Type a URL into the search box.
You will then get suggested sites (unless the URL is too obscure).