After last year's original versions of Avatar (in 3D and 2D), and this year's extended Special Edition, comes an even longer version, the Collector's Extended Cut, available on video in 2D. The Special Edition featured eight minutes of additional footage; the Collector's Extended Cut adds a further eight minutes of material, making it sixteen minutes longer than the original version.
Additions to the Collector's Extended Cut include an explanation of why the school (introduced in the Special Edition) was abandoned, and a rather dark and violent prologue set on Earth (with lots of rain and neon, like Blade Runner). This prologue is tonally different to the rest of the film, and I therefore prefer the original version. Generally, the additional footage in the Collector's Extended Cut is narratively less significant than that of the Special Edition.