You can post your articles on other sites. But if you create an unique article , then why don't you post your content on your site alone? (I prefer to modify it a bit and post it on article directories.)
The following is in Google help section:
Syndicate carefully: If you syndicate your content on other sites, Google will always show the version we think is most appropriate for users in each given search, which may or may not be the version you'd prefer. However, it is helpful to ensure that each site on which your content is syndicated includes a link back to your original article. You can also ask those who use your syndicated material to use the noindex meta tag to prevent search engines from indexing their version of the content.