I’ve actually started up a project on github called yql-tables to store useful table definitions and will be taking submissions from the community. You can try them out by ‘use’ing them directly from the git repository or by pulling them onto your own server accessible from the YQL servers.
Read more about YQL and custom schemas on Sam’s blog. The repo has only been up a few days but @davglass has already contributed a schema for GitHub. Follow his lead and share your YQL table definitions for the good of mankind!