Overall though your site will NOT be penalized for having content on it that is available elsewhere. Rewritten content will get you better results though.

When you submit content to any site, including your own, it will always get more reads when it is new than when it has aged. Promotion of your pages, articles and sites is an ongoing task that never ends. There are ways to make the job easier though. I confess, I find using content to build my business seems the easiest and most reliable method see more of promotion as it is doing the very thing that search engines seek out - new stuff for people to read, listen to or watch.

One final point, always try to promote your promotions! If you have an article on another site then either link to it from somewhere, or easier and maybe better, take an rss feed from the site that contains your article and submit it to a raft of rss aggregators and directories, it only takes a couple of minutes to do and will benefit your target site by providing a network of links channeling back you your own main site and page.

So, content absolutely rocks, it is king, queen and emperor!
I hope this helps!