DVD Buying Guide
Contains a region coding FAQ and a map of DVD regions.
http://www.dvdbuyingguide.com/

Kropla.com
Tells you which TV system is used in the UK.
http://kropla.com/tv.htm

World Video Formats and Standards Conversions
A quick-reference guide to television broadcast standards around the world.
http://www.video-pro.co.uk/worldtv/index.html

Worldwide TV Standards
A guide to video formats worldwide.
http://www.ee.surrey.ac.uk/Contrib/WorldTV/video.html