Electronics
OpenDCC Project
OpenDCC is an open project to implement DCC with standard electronic components, it is mostly based on the AVR microcontroller.
Currently a lot of the site is in German, I think you can help with the translation if you like.
Model Railroad Hobbyist Magazine
A Professional FREE 3 monthly online Model Railroad magazine directed at hobbyists.
Magazines are designed for downloading and reading on your computer rather than being printed out.
Model Railcast Show
A Model Railroad focused podcast/blog. For railroading beginners and seasoned line veterans.
The Model Electronic Railway Group
An international, UK based group promoting interest in the application of electronics (including computers) to all aspects of railway modelling. 
C/MRI: Computer Model Railroad Interface
The home of Dr Bruce Chubb's C/MRI: Computer Model Railroad Interface.
This is an extensive set of input and output control boards for allowing control of a model railroad from a computer.
