Which site is better at finding this page, that I knew I'd seen linked recently but couldn't remember many details of?
Google: http://www.google.com/search?q=css+button
Feedster: http://www.feedster.com/search.php?q=css+button
or del.icio.us: http://del.icio.us/tag/css+button
It's a bit of an unfair test, as I'd probably only seen the page because it was popular on del.icio.us recently, but it does show that the del.icio.us system is surprisingly good at picking out the most important keywords or concepts from a page.