As discussed by many others (      ), Google announced a new feature rather boringly named "Google Custom Search Engine" that allows anyone to "create a search engine that reflects your knowledge and interests; looks and feels like your own; and ... make money from the traffic you receive."
The actual implementation is not quite as grand as that. As Greg Sterling said, it is basically "industrial-strength Rollyo" where people can limit to or favor search results from specific domains and bias the search results to favor matches to given keywords.
Even so, it is fun and let me easily test an idea I had been kicking around to bias search results to sites that provide high quality answers like Wikipedia. Here is an example inline:and here is the same custom search hosted on Google. Try a search like [San Francisco] on this custom search engine and compare to the same search on Google. Medical searches like a search for [arthritis] also seem a bit more useful to me.
This custom search takes the bias Google Web search results seem to have toward Wikipedia a step further. It also favors a few other sites that focus on providing answers. The results are pretty good for questions and requests for factual information, but it obviously is only a twiddle on top of what Google already does, and it does not help for all types of queries (e.g. navigational queries).
By the way, it is not obvious to me that a bias toward Wikipedia or other sources is the right thing in the general case. The existing ranking algorithms already attempt to bias toward authoritative sources. At best, if you like these results better, it might mean that a few particular sources should be considered more authoritative than they already are.
In any case, it is fun to be able to play with this kind of thing so easily and quickly.