Google, Yahoo! and MSN (Live) all have webmaster tools that require users to verify that they control the site, either by uploading files, or by adding meta-tags.
I never liked adding meta tags, and I found it hard to keep track of whose accounts the uploaded files pertained to (in case I ever wanted to revoke access - not that it matters much). So I wrote a small plugin to handle verification files and keep track of the codes in a single yaml file.
Nothing ground-breaking, but saves a little time if you work on lots of small sites and also handle seo tasks.
http://code.google.com/p/search-engine-webmaster-verification-rails-plugin/
Jeff Dean