Big kudos to Barry Welford who pointed out Keotag at Cre8asite. The site offers a simple search tool for single-word tags (or combinations of them). It allows for direct, quick queries to 17 different "web 2.0" type engines (and Google), including Technorati, del.icio.us, Newsvine, 43 Things, etc.

The interface is nothing remarkable, but it's easy to use, fast and, as I've been noting with many of the social tagging/blog search sites, returns far more timely and interesting content than your standard web search engine. It doubles as a decent competitive analysis tool, assuming you look in the right industries (tech, financial, webdev, search, photography, etc.).

Sample Keotag search for "seomoz":