I just found a great Polling WebPart from Phil Wicklund. You can find it in CodePlex or in his personal site to check for working examples, screenshots etc. It works great in my last project. There are some restrictions (in current release), like the poll submitter can submit twice/ more and max 5 poll questions / answers. But it can be customized according to our requirements. Phil has given the source code too. Just download it from CodePlex. In order to use it, just use the stsadm.exe command tool (read this tutorial by liedong). All the credit goes to Phil Wicklund. Great Job!
Here are some screenshots taken from Phil's website.