Unless you've got an Apple TV or computer next to your TV, your purchased iTunes movies are limited to your monitor. Wired details how to burn those movies to a DVD for the bigscreen experience.
Their method involves removing the DRM copy protection and burning the resulting file to a DVD using a couple of shareware applications, namely Tunebite for DRM removal and Aimersoft DVD Creator to burn the DVD. We're not keen on the cost of the software (Tunebite does offer a free trial), but if it's something you've been dying to do, Wired's guide could do the trick. Still, the DVD burning software they highlight doesn't appear to do anything you can't get from a free alternative, so you could probably save yourself $US35 using something like previously mentioned DVD Flick to burn your DVDs after removing the DRM.
If you've ever been down this road and have your own methods, let's hear how you burned your iTunes purchase to a DVD in the comments.