Wot is it? Twitterspectrum
At this address: http://www.neoformix.com/Projects/TwitterSpectrum/TwitterSpectrum.html there is a great toy. It lists two interlocking tag spectra if given two words. This example shows the tag spectrum for the two words 'architecture' and 'window'.
The overlap area is for 'architecture' OR 'window' AND 'tag keyword'... not quite what I expected to be the content out. I had hoped assumed that it was showing overall keyword + tag on the left and right and in the middle both keywords + tag...
Still - a search engine for twitter based upon content not person's name is great.