Where can I find how people find my site?
Hittail is a tool for understanding search traffic put together by the folks at Conner Communications. It is elegant in its simplicity -- it takes search strings, parses them into key words, ranks them into the head and tail, and then makes suggestions about how to improve traffic to a site.
It's a hosted site and all that is required is placing a snippet of code on a site. Free for small sites, reasonable for the rest of the world.
Very useful indeed.