This site http://ac6v/antprojects.htm#theory was already posted, but there are a few more gems out there:

http://www.universal-radio.com/catalog/mwant.html

http://www.w5yi.org/page.php?id=25

http://www.fcc.gov/encyclopedia/rules-regulations-title-47

http://www.dxzone.com/catalog/Antennas/Homebrewing_Techniques/

http://www.arrl.org/arrl-antenna-book

Here is the bottom line for those who don't already know... be aware of the laws in your country before attempting to operate a broadcasting transmitter. Commercial stations pay for their air time so they have all the rights, you have none. Don't step on a commercial station or you could be heavily fined, your equipment confiscated and/or jail time.

 

Hello,

Here is a page with some more links:
http://www.101science.com/eleclinks.htm#11

Bertus