Amazon UK have a pretty decent special offer on at the moment, with 3 for 2 on approx 70 titles including some great movies such as Close Encounters, and many more.
Check it out: Amazon.co.uk
UPDATE: Amazon have now added Indiana Jones, Kung Fu Panda and WALL-E into their 3 for 2 mix.
* The Dark Knight (Limited Edition) (Warner)
* The Dark Knight (Warner)
* Dodgeball (Fox)
* Dumb & Dumber (Warner)
* Horton Hears a Who! (Fox)
* I Am Legend (Ultimate Collector’s Edition) (Warner)
* Jet Li’s Fearless (Universal)
* Lost: The Complete Fourth Season (Buena Vista)
* The Mask (New Line)
* Ray Charles: Live At Montreux 1997 (Eagle Rock)
* The Strat Pack Live in Concert (Eagle Rock)
* Super Troopers (Fox)
* Tori Amos: Live At Montreux 1991/1992 (Eagle Vision)