The browser cache is a largely untapped treasure of personally relevant, high revisit probability content.  Opera 9, as pointed out by Simon Willison, is the first browser to support offline browsing from the browser cache.

There's more that can be done with the cache... check out this project that enables a fly through the cache, selecting text and image excerpts, to allow interesting content creations and a more tangible way to engage with you browser history.  (In general, user's report using browser history functions even less often than bookmarks).