I always like to find interesting new search engines and www.websiteslike.org falls into that category. Just type in the URL of a site that you like, and it will find other similar sites for you. There are a few of these products out there now and my favourite remains SimilarPages because of the nifty little app you can get. There's also SitesLike as well. Or, if you prefer Big G, try related: although they've hidden this function now because, well, they don't want to help people find stuff do they.
Anyhow, back to this one. It claims to have listed over 1,000,000 sites and I tried it with a couple that I know and I was happy with the results that it returned. Give it a go next time you're stuck