You can add surveys to the free version of WordPress by navigating to Polls from the sidebar. You’ll have to sign up for a free PollDaddy.com account to use them, and you can also use the PollDaddy plugin for self-hosted WordPress sites.
On the self-hosted version of WordPress you can install the Polldaddy Polls and Ratings plugin and do the same thing. You’ll still need a Polldaddy account to use it – but it’s free and easy to setup.
Checkout Polldaddy.com for more information – it’s made by the same folks that make WordPress, Akistmet, VaultPress and other great services.