As you browse it caches and indexes local copies of webpages so that you can search through them later, and even view the cached version if you’re offline. It strips the pages of all HTML except for simple paragrpahs, presumably for easier search indexing, which means no CSS o images, so the cached version is as plain as can be, but this is a fair exchange for disk space and proxy speed. It’s written in Python and uses (I think) PyLucene for the indexing, and is, as a result, very quick. Additionally, since it just uses a query parameter on the search page, it’s very easy and quick to set up a Firefox keyword so you can search from the address bar: I just type “find dvd” and up come all the pages I’ve viewed with “DVD” in them, ranked by relevance.
Simple and does the job, I don’t think praise gets much higher than that 🙂