There are a small number of search engines that allow you to find alternative and similar webpages and SimilarSiteCheck is the latest one. I've taken a look at it, and have to say that I found it really rather frustrating. The concept is simple - pop in a URL of a site that you're interested in, and it will find similar sites for you, based upon its interrogation of the site that it's been given.
On the plus side, it did come up with some interesting sites when I ran a search for Google UK, and I found some interesting sites that related to my football club, but it was less helpful when I tried the CILIP website (no alternatives), the BBC (again, no alternatives) and it took forever to undertake a live analysis of the UK ebay site. A search for my own domain led to it suggesting lots of sites for me that were produced by other people with the same surname, which didn't impress.
I was also very disappointed in the display of results. They're using one of those really annoying social media menu bars on the left hand side of the page that totally obscures what you're trying to look at:
Seriously - how is it possible to be less helpful? Well actually I can tell you - the links to the alternative sites are not live. That is to say, if I want to visit any of them, I have to cut and paste the URL myself. What's irritating is that they can do it - the original site that you put in as your search term has a call out box - but I already know what is on that site - it's the alternatives that I need!
To be fair, there is a bookmarklet that you can add to your browser, but that's not much help when the results are middling to poor to non-existent. It's worth keeping an eye on it, because it can only improve, but until then, I think you'll need to visit SimilarPages, SimilarSiteSearch, or possibly Siteslike.