I've wondered when web engines were going to begin offering the following type of service. Today is the day.
Something new and potentially very useful from Matt Wells and the Gigablast team: Build Your Own Topic Search Engine.
Gigablast now allows you to create a search tool that searches only the sites you tell it to (using the Gigablast web index). You're able to select up to 200 urls (or subsites). In other words, you can easily create your own subset of the complete Gigablast index.
Simply copy and replace a few lines of code, list the urls of the sites you want your topic engine to search, paste the finished code into a web page, and you're done. You do not need to register and you can create as many topic engines as you like. Very cool!