I'm not usually a great fan of browser add on tools, since you're limited not only by the browser itself, but also the machine that you're using. However, I do use a few of them, but they have to be really top notch. I was introduced to SimilarPages today, and as it required installing onto Firefox (and doesn't yet work on any other browser, though an IE version is in the works) I wasn't overly keen on it. However, I had time available, so thought I'd give it a go.
The concept of SimilarPages is pretty obvious - the clue is in the name. It's a tool that finds pages that are similar to the one that you're looking at. There are plenty of ways of getting data like this - Google has several, including the Related: function, and there's a very nice search engine that I've written about before called Web Insuggest - if you haven't tried it I would most certainly recommend it. The disadvantage of both approaches however is that it's necessary to go to the page/resource to find others. SimilarPages works rather differently, and this is where the download and integration into the browser is important. There are three ways that you can find similar pages:
Simply click on the icon and get a sidemenu display. You get a lot of alternatives, and I was very impressed with the choice for my CILIP example; you get given up to 300 options. I recognised a lot of the sites (and would have listed them myself as related sites if asked) but many I didn't, and a disadvantage is that I'd need to click on the link to go and have a look. A mouseover of more than the URL (which I can already see) would help. The menu bar stays open when you go from tab to tab, and it's lightening fast however - very impressive.
Alternatively you can right click on a page and get an inscreen menu option:
Overall, I like the service. It integrates very nicely into the browser, it appears to be very accurate and it's quick. I'd like a clearer indication of where the links go however, as discovery by click isn't ideal. I think it's worth trying, if you use Firefox and one computer.