I appreciate your work on this (in the past I've just used google with the site option). As a nitpick, one thing I'd do is remove the fluff from the bottom of the page and give an indicator that the large box is for a search term (as opposed to several lines of text which is what it looks like). In fact, a normal sized box would work just fine.

I realize that there is a line that instructs you to enter text in the box, but to me in got lost in the noise of the page (another reason for getting rid of the extra details at the bottom). On the results page, it'd be nice if you showed the results foremost and the related topics as a sidebar. I want my results, and only if I don't find what I'm looking for do I want to know the code's opinion of where I should try to go next.

Anyways, like I said those are just nitpicks. Nice job.