While search engine clustering is very common these days, few do it better than brainespot. Clusty and IceRocket are two examples of more recent engines that allow you to search the top services like Google, as well as reference sites such as Wikipedia, and even the world of blogs.
And speaking of blog search, what is the deal with Technorati these days? I can understand that such a large dataset can be a challenge to query, and the system gets an enormous number of pings each day for new content, but they really have to do something about reengineering their backend.
But I digress. I don't know that much about the history of brainespot, or who's behind the programming, but I must say they have some of the best results I've seen. At least for technical topics such as is the nature of this Web site and my particular obsession.
drx for instance, provides canned search links to a bunch of different engines at the bottom of every category, including the aforementioned Google, IceRocket, and a bunch of others (including searching blogs, social bookmarking sites, etc.) Recently, I added brainespot to the list. And I must say I'm very impressed with the results you get. You can even set preferences for clustering methods, the level of detail in the results, whether links open new windows or not, search time threshold, and adult content filtering,
Give it a try sometime.