Ditto that -- there have been several posts and comments where people on the site have wanted to conduct a poll, but have been unable to do so in a gracefully and straightforward matter. The "you be the jury -- Amanda Knox" thread, this comment by E.Y., and Help Roko Become a Better Rationalist are all examples of this.

Since we already have a wiki running, note that votes take place on wikis all the time; such as the current round of voting on the Wiktionary logo. Maybe the standard policy could be to set up a poll on the wiki and point to it on the main site, and make templates and scripts available to make this easier for everyone. It'd also make the wiki more visible.