The vast majority of visitors here are socially referred from sites like HackerNews or Reddit. Twitter, Google reader, and direct visits make up most of the rest of the traffic. I realize my blog is fairly small as far as traffic goes (140k visitors in the last year), but it's noteworthy how search appears to be the most random source of visits, contrary to what I'd expect.
Once or twice a year I write a post that somehow latches on to popular search engines. From the time of that post onward, it'll get traffic each day from keyword search. The first of my search posts was How to embed Google wave on your wordpress blog. Since late last year it received a steady stream of 100 or so visitors a day for 5-6 months diminishing in spring as Google Wave subsided. I did nothing to update the post and it remains much the same as the day I wrote it, the exception being blog design overhauls.
This year's search post is Holy Crap Minecraft! This post receives 200+ search visits a day from a range of keyword searches about Minecraft. I took a different tactic for the page though. The first experience with my blog for a few thousand visitors a month will be that page, I might as well make their visit awesome. Now once a week or so I look for updates or an incredible video about a creation in Minecraft and add it to the post. These search nomads may never know anything about this blog or who I am, but at least they'll get fun, timely, and relevant content while here.