Technorati allows simultaneous searching of multiple tags using 'OR' in tag

Technorati is one of the top spots for tracking what’s going on in the blogosphere about your favorite topic.  Bloggers just add technorati tags to their posts (blog categories are also considered tags), and users can then search for blog entries tagged with specific keywords.  Previously, you could only search for one keyword at a time, but now Technorati has implemented Multiple Tag Search.  Simply enter each of the tags with the word OR in between them. 

From their site:

 Multiple tags are a great way to follow your favorite topics while accounting for the variety of methods people tag their posts. A tag search for college OR university displays the latest posts indexed by Technorati tagged with either "college" or "university." You could also mix tags in an area of interest such as tracking the mobile gaming industry through a tag search for PSP OR GameBoy.