While doing a quick research on the topic of "comparison shopping", I came across not only the obvious comparison criteria like price, reviews, user submitted ratings, popularity etc. but also more exotic ones like alonovo.com that allow prospective buyers to look at the behavior (use of green tech, contribution to local community etc.).<p><a href="http://charteo.us/" rel="nofollow">http://charteo.us/</a> allows comparison of popularity, as measured by Amazon Sales Rank, over a period of time (Full disclosure: this one is my baby and inspiration for this research).<p>What other exotic comparison shopping startups/sites have you come across?