“5 Web Files That Will Improve Your Website” @ Six Revisions
I have recently bumped into a cool post by Alexander Dawson that treats about five files, that will complete your website. Four of them (robots.txt, sitemap.xml, dublin.rdf, opensearch.xml) are strongly connected with search engines, while the fifth is a well-known favicon.ico file. I recommend reading this article even if you are not quite interested in Search Engine Optimization.
http://sixrevisions.com/web-standards/5-web-files-that-will-improve-your-website/