There are of course, other options out there, but the original poster specifically wanted to know how to stream iTunes movies. I am assuming lukacs46 doesn't want to have to go through the pain of transcoding everything and just wants to hook up a box and have it work.
For me, ATV does just that although some people have had issues and go with alternative setups that cost more in either money (Mac Mini) or time (re-encoding content). I stick with the simple approach and absolutely love my ATV!
It's true that there are video/audio streaming devices that are cheaper than the Apple TV. However, those $100 devices don't include a hard drive or WiFi so if you need to add both of those items to your setup then the Apple TV may in fact be a cheaper option.If all you want to do is stream movies, there are a lot of little cheap media streaming devices available now that have pretty decent capabilities. Most are in the $80 to $100 range and you can get units from Asus, Patriot, Western Digital, etc. They're all pretty similiar in basic functionality...