Free site-search service Buildasearch does exactly what it purports to—combine a bunch of
site:whatever.com commands into a single search box. Beyond just bookmarking a long Google URL, however, Buildasearch offers customised logos, colours, and layouts, and seems to return results pretty quickly. The interface (and translation) can be a bit rough, but the end result works as promised. You can keep your custom search on Buildasearch's servers, or use their API to install your search on any server that supports PHP. It's a handy tool for those who find themselves digging through the same collection of sites repeatedly.