One of the best free content sites I have found is www.contentinfusion.com. Not only does it offer quality articles, but the options for formatting those articles are much broader than most content services. You can even have it display thumbnail images next to each article, which is something I have not seen in another service like this. The categories are a bit limited still, but if your site falls within one of its categories, you could have a good new resource for offering dynamic content on your site.