Raffler provides a way to raffle among attendees of your meetup.
We at Slovenia Ruby User Group have several things to give away each time, so we made a simple app that raffles n people from everyone who attended on meetup.com. You can just go to the website, input your meetup.com Group URL Name or ID and select the meetup. Here's an example for our October meetup. You can deselect the people you don't want raffled (like organisers) then input the number of the rewards you have and click Raffle. It's that easy.
BTW PRs are wellcome!