topr8 - 6:36 pm on Mar 3, 2010 (gmt 0)
That couldn't be easier.
Go to any page that has a search box on it. Right click in the search box and choose Create Search...
exactly it couldn't be easier (and has been like this for a while), i even have added the site search for my own main site.
the only annoying thing is that it wants you to create a keyboard shortcut at the same time and maybe i don't want to do that, i'm happy with the dropdown list