The only thing that you can do is to post links on as many sites as you wish, but you cannot post the article itself. It must only be on HubPages and nowhere else. Even if you publish first on HubPages and then on another site. Citing a reference that it was first published on HubPages does not work!
A way to get around this is to edit (change) the article; different words a different spin and so on.
HubPages prides itself in only having original content and Google frowns upon what they consider duplicate articles.
This was intituted about a little more than a year ago and you can read more by visiting the help section under the TOS