If you are reading this and don't know the plotline then where have you been for the last decade! It is basicly a spin-off of the movie of the same name. it is set in a future where the line between man and machine has become blurred and follows a team of police officers/para-military types lead by a full cyborg known as the Major.
The shows real beauty is it's fantastic plot's and very intellectual and philosophical tone. It also has some beautiful animation and some of the best characters you will ever see.
All in all this is an excellent show and one that I think everyone should see at least once.