Through today only, October 30th, Vudu is offering FREE $2 Vudu Credit. All you have to do is watch FREE movie with ads from their selection. There are many movies to choose from, you can check in their list here.
Note that to be able to get the $2 credit, you must finish watching the whole movie before midnight PST and your chosen title must not be in your Purchased library. Once you meet these requirements, a code will be sent to your email by November 4th.