Turn off Nautilus. I’m not kidding. It’s that much of a bloated pig. Sure, you won’t have icons on your desktop, or use the file manager, but to be honest, I never have. I think I’ll lose some stuff with drag and drop, but I’ve never used it anyway. The performance increase is noticable.
Run gnome-session-properties, pick the current session tab, highlight “nautilus”, and click “remove”. Then click “apply”. If you don’t like it that way, you can just run nautilus from the command line.