I love wordsmith.org. A long time ago I signed up for their email list, and Monday through Friday I get a fun email about words, their history, useage, and even a link telling you how to pronounce it. Today's word is "shirty." It means bad tempered or irritable.
I'm afeared if people said it quickly too many times in a row it might get them into trouble in polite company.
Besides the fun books you read, are there any good sites you go to that broaden your vocabulary?