A new built-in poll system is released today. You can activate the poll feature on a per forum basis. Just go to the forum settings and enable it in the Advance Settings part of the page.
A couple of caveats:
- Polls automatically end after 30 days
- You can modify when the polls end by specifying the end date (currently you need to edit this to modify the end date)
- Admin can restrict poll creation / editing to moderators or to the general user base