Logophilia, home of the Word Spy [1]. Each weekday they post a new word, and a citation to show how it people are using it. The Random word spy [2] sounds the most interesting waste of office hours toy, alas it is not working right now.
another great site to visually stimulate your wordy self is the visual thesaurus [3] which I found whilst surfing dabitch's own little site. ty dab!
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Links:
[1] http://www.logophilia.com/
[2] http://www.logophilia.com/WordSpy/RandomWord.asp
[3] http://www.plumbdesign.com/thesaurus/index.html
[4] http://technorati.com/tag/advertising news