What kind of photography are you interested in? With portraiture, you're going to want/need lights. At least one speedlight that has a swivel head. You can get prints made almost anywhere, so not the printer unless you plan to print everything. Along with a flash, you're going to want/need some light modifiers, stands, and a way to fire the flash off camera.
What lenses do you have now, and again, what kind of photography do you want to do?
Editing software is pretty much a must-have for any type, assuming you are working with digital files.
A tripod is something often overlooked, but when you need it, you need it. Along with that, get an inexpensive cable shutter release.