I've been working all morning on a cover letter for a new job, and after a couple hours of fine tuning I realized I could, through the Speech service, have the OS read the letter to me (select the text in any Coca application, then select Services -> Speech -> Start Reading Text) . This was a great help and I caught a couple typos I hadn't previously noticed.
[Editor's note: Yes, this is a fairly basic hint, but items in the services menu are often overlooked, so I thought it was worth a mention!]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20021107062418187