Dungeons and Dragons 4th Edition was released in mid-2008. However, the current list of Rules Updates only has one from October 2010. Are updates really released that infrequently, or are there other places that updates are posted?
Updates seem to be about monthly. They list the most recent update as a unified package for all updated books, and keep an archive by book being updated.
Check out the Rules Updates Archive at the bottom of the Updates page.