I've had this thing around for nearly two years and have just not known what to do with it.
Google was doing a pretty good job with search results as long as a topic didn't have a profit motive associated with it. On popular, money-making keywords, the top ten are polluted by the SEO consultants.
What to do?
One option is to use the Google advanced search to limit the search results to recent content. The SEO dudes haven't colonized this territory yet. But this only gets you so far; sometimes you want all of the results.
What else could work?
Well, a mashup between Google and Delicious seemed pretty obvious. But messing with Google search results is a no-no.
How to get around this?
Simple -- let the user do the reranking using a bookmarklet and JSONP.
Thus Rerank was born. I use it on a daily basis to improve my search results. Everyone I have exposed to it has been pretty jazzed by it. Thus my dilemma: I can't scale the backend right now because it depends on del.icio.us, which throttles calls from a single IP.
So, I'd like to show off this idea, but if more than a half dozen people use it at a time, it stops working. So I've been sitting on it for all this time.