After reading this post on Strobist, I finally found a way to get sitewide search capabilities for the great price of $0! Now, instead of somebody having to go to Google to find something on my site (or click through many archive pages... a very cumbersome process!), he can simply type in his search in the little search box at the top of the page. Quite intuitive—kudos to Google for this!
The only problem I'm having (which I hope to resolve soon) is on the results page; there's an inordinate amount of extra white space after the search results and before the page footer; does anyone know why this might be?
If you'd like to put a customized Google search box on your website, visit Google Custom Search Engine.