Rollyo enables you to build your own search engine.
How it works:
Build a "searchroll."
A searchroll is a list of sites that you trust. Add all of the Websites on a given topic that you want to the roll. You can assign a general category for the roll, and apply "tags" to describe the topic.
Share searchrolls with others
Other people can search your searchrolls, and you can search theirs to discover new Websites about topics that are important to you.