I've said many times before that headlines are one of the most important elements in your newsletter because they act as salesmen for your articles. Writing a good headline will increase the chances of your article being read.
Newspapers spend a lot of effort on headlines. They have editors who specialize in writing them.
The Newseum, the new museum of the news in Washington, D.C., allows you to search through an archive of past newspaper front pages. It's a great way to get ideas for headlines. Try choosing a headline and then substituting words in that headline for words relevant to your article to make a new headline that really sings.
(Thanks to the 37 Signals Blog for flagging this.)