This is one of my top favourite movies. Not only the plot is incredebly clever and intriguing, the photography is also stunning and one of the few movies where special effects actually add to the story rather than distracting from it.
In a nutshell, having discovered a way to break into other people's dreams to "steal" ideas, a group of "criminals" is assigned a mission going in the opposite direction. They must "implant" an idea, which makes their task even more difficult. Since in dreams we live forever, the task is complicated even further by a dead woman who just does not want to stay dead.
You can watch it over and over and still find something new in every viewing. Definitely recommended.