GhostInTheShell takes place in a future where computer, android, and cybernetic technology have all become highly developed. Key to GhostInTheShell is the concept of a "Ghost" - the collection of feelings, intuition, memories, and other things that makes people people. Except that the Ghost isn't just a philosophical concept, it's something people have verified the existence of. Ghosts can be hacked, leaving someone with false memories. They can be copied imperfectly, called "Ghost-dubbing" and usually done on a large scale to give service androids a touch of personality.
The main character (in both mangas, the movie, and the series) is Major Motoko Kusanagi. She's a woman who's replaced her entire body with cybernetic parts; the only original parts she has are her brain and spinal cord. Therefore, she still has a ghost. She's also one tough cookie. :P She works for an elite antiterrorism unit called Section 9. In the first manga she goes through various missions before getting to the meat of the series; in the movie they put in one mission and got straight to it, since they didn't have as much time. In both the first manga and the movie, she meets up with a mysterious Ghost-hacker known as "The PuppetMaster?". She discovers his real identity, and much philosophy ensues. It's a lot more bearable in the manga than in the movie. Things to credit the manga and movie with? They make you think, AND they have cool action scenes.
In the manga, crab-like mechas called "Fuchikomas" are fairly important. They're also really cute. There's one section in the manga where one of the fuchikomas tries getting the others to revolt, but fails because they can see no advantage in revolting. There are no fuchikomas in the movie. (Booo!) The TV series has Tachikomas, which are like Fuchikomas except cuter and less armored and stuff.They also have kids' voices. The only way they could be cuter is if they were pink. (They're blue.)
I haven't read the second manga series, so I don't know what's in it. I haven't played the VideoGame, so I don't know what's in it, although I think it has to do with Fuchikomas.
The series, GhostInTheShell: Stand Alone Complex presents an alternate reality where Motoko never meets up with the Puppet Master. It is released only twice a month on pay-per-view cable in Japan, and the makers aim for a complete run of 26 episodes. Several episodes (half or more so far) are stand-alone; you can watch them without really needing to watch what came before or what comes after. They still manage to make you think, and have awesome action scenes. The really good parts, though, are the intermittent chain of related episodes, all having to do with a mysterious hacker known as "The Laughing Man". (Since we've been promised that the PuppetMaster? never appears, the LaughingMan? is not the PuppetMaster?, even though they seem awfully similar.) Also, the soundtrack is by YokoKanno, who did the CowboyBebop soundtrack and numerous others.