I’m going to start using searchmash.com as my primary search interface. It’s basically an unbranded testbed that google uses to try out search source aggregation and ajax features such as autocomplete and dynamic results retrieval. My favorite feature is the Wikipedia search, which is an example of search source aggregation. I guess it’s sort of like dogpile, except that it’s useful.
Here’s the OpenSearch source for the plugin: http://ankur.org/xml/searchmash.opensearch.xml

Click here to install the plugin.