First off, a Google for "Article Directories" is a great way to hunt 'em down if you have the time.

I have a list of several sources that seem to work well for me, with Steve's recommendation being just one of them.

Here are a couple more:

www.articledashboard.com

www.articlesender.com

www.articlemarketer.com

www.goarticles.com

Alan Says also has set up a brand new article site you might want to check out too! http://www.warriorforumarticles.com

Good luck!

Pete