Suggest me a Voting / Polling tool

Hi All,

Can anyone suggest me a voting / polling tool to be used for photo
contest. It is fine if I link out to their site. I want to upload all
the photos, and allow visitors to vote ONE TIME only. I think this
would be a part of the tool, and also there is some sort of mechanism
in place to safeguard as well as possible keeping people from voting
more than once.

Thanks in advance.

Regards,
Suresh P