I created a Firefox Addon and website for it last year that did everything you just wrote about, but I've since closed the project down. Let me know if you or anyone is interested in resurrecting it.
It's not open source. The Firefox Addon captured a visual snapshot and the entire page contents of every non-https page you visited, and stored it to an online database. The website allowed you to search your history, and results were based on number of visits to a page, length of time spent on page, number of times that page was selected as a search result, whether the page was actually bookmarked, etc. It was a very useful tool, but unfortunately the database grew large very fast. I tried to implement a subscription feature to offset server costs, but I had zero subscribers.
The code is all C#/MSSQL/JavaScript/XUL. If anyone's still interested gmail me at my username, and sorry for the off-topic posts!