I came across the Google Co-Op search today and decided to set up a 'search engine' of my own. It allows you to add a list of your favourite web sites (relating to a particular topic) and then either get search results exclusively from those sites or prioritize those sites over the 'standard' Google search results. I've got mine setup in the latter mode at present, because I know I've forgotten some sites. It also wraps up the whole thing into a nice ajaxy interface to embed on your own website - check out the boogdesign Web Technology Search.