These links are already in the footer of the page, but I only noticed these because I was specifically looking for them ("there must be a link to serverfault somewhere..")
They really should be more prominent..
On a pedantic note, you don't need to re-include jQuery because Stackoverflow already uses it, so you can simplify the Greasemoney script a tiny bit and remove..
Updated to include new Search (Search Meta/SO/and SF all together)
Adds links to the top, and updates regular search to "Power Search," which will return results from all of the SO sites.