During the last days, I was working on an introductory paper on how a GSM cellphone actually works. It is titled Anatomy of contemporary GSM cellphone hardware and should provide a good technical text for anyone who generally is into technology and understands a bit about both software, computer architecture as well as radio, but who still feels like he has no clue what is actually happening inside the phone, particularly the hardware side.
The text does not cover the GSM protocols itself, as there is much more information available on this already.
Feel free to let me know what you think, I'm always happy to extend or clarify it based on your feedback. I hope some people find the text useful.