Well i was just thinking to write a NES emulator since 2008 but that time i could not start due to my game engine. But now after learning these tutorials i must say anyone can make emulators who understands Microprocessors.
Please go through these tutorials to learn emulation. The tutorial is well written, small and very understandable. I will also write tutorials the way i feel simple once i do my NSF player.
Link: http://codeslinger.co.uk/pages/blog/wordpress/