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, usage, and even a link telling you how to pronounce it. A while back, the word was "shirty." It means bad tempered or irritable.
I'm afeared if people say 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?
And don't forget about the iWriteNetwork Summer Workshop! You can register on the right of this blog post.