Eric Enge is quick out of the gate with Custom Search Guide, which is a directory of Google Custom Search Engines.
And the AJAX search API folks whipped up a quick example of blending the Google AJAX Search API and a CSE. It’s got four CSEs on one page (product reviews, price comparisons, forums/message boards, and shopping). Then from the AJAX side, there’s blog, web, and news search, plus a strip of related videos at the bottom. If you haven’t seen the latest examples of the AJAX search API, it’s worth a looksee. My favorite is the mash-up of search + a spreadsheet + mapping on this page. You could also use that page to generate phone leads, for example.