Apple is said to be preparing iTunes 7.6 for release at Macworld on the 14th and 15th of January, this update to the media / music manager will add Movie Rental support, with movies being available from 20th Century Fox and Walt Disney Studios.
The movies are said to be time limited, in that they expire 24hrs after the time of purchase, and should retail for between $2 - $5 (£1.04 - £2.60 Approx').
Also some DVDs are beginning to ship with iPod / iPhone compatible copies one such DVD is Family Guy, as shown on Macrumors.com