Very good

I wanted a free plugin as I was only wanting to run one contest. I found Social Boost to be really good as it’s user friendly, has plenty of options, looks good and is relatively simple to set up. It also integrates well with Aweber. The support team are really good too. My only gripe would be that the free version only allows you to have up to 50 entrants. After that, you have to pay if you want to be able to select a winner. Would definitely recommend though.