Here are some useful badminton links:
The official website of the national governing body of badminton in the US.
International Badminton Federation
The official website of the governing body of international badminton.
A very good all-around badminton website.
Probably the best badminton website out there, albeit slow.
San Diego Badminton Supply
A very good source of badminton supplies. 3-day delivery. Highly recommended.