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).