The original Ghost in the Shell movie was released in 1995. In 2008, a remastered version called Ghost in the Shell 2.0 was released.
Are there major differences between these two versions and what differences are there?
To add to Joe L.'s answer, the website Movie-Censorship.com has a detailed list of every difference between the two versions.
Note that the CGI for some scenes was changed, the general "tint" of the movie went from bluish/greenish to orange, some of the audio was changed, some voiceovers (like the Puppet Master's) were redone by a different actor, and some minor scenes were cut.
In my opinion, the remastered 2.0 version is very inferior to the original. Yes, the CGI in the original was clumsy, but everything else was superior, including using 2D animations for Kusanagi's action scenes. And seriously, how can anyone think the CGI chopper is superior to the original, beautifully painted 2D chopper is beyond me :(
Just take a look. The original chopper, in beautiful 2D:
and the awful CGI version:
According to this Wikipedia entry , "It was re-released in 2008 as Ghost in the Shell 2.0 with new audio and updated 3D computer graphics in certain scenes." It sounds to me like it's the same movie with a few graphics tweaks, a remastering of the original rather than a remake.
On the Ghost in the Shell wiki (there just had to be one) :
Ghost in the Shell 2.0 (GHOST IN THE SHELL／攻殻機動隊 2.0, Gōsuto In Za Sheru/Kōkaku Kidōtai 2.0?) is a reproduced version of its original 1995 counterpart. It was produced in celebration for the release of The Sky Crawlers in 2008. For the films Version 2.0 release, all the original animations were re-produced with latest digital film and animation technologies, such as 3D-CGI. The original soundtrack was also re-organized and re-recorded.
So, it's the same movie with updated graphics and audio.