Includes a little theory behind baluns, and how to build them. Covers the choke balun, Collins balun, transmission line balun, bazooka balun, and VHF balun.
http://www.qsl.net/iz7ath/web/02_brew/11_balun/pag01_eng.htm
A transmission line transformer for converting balanced input to unbalanced output or vice versa...
http://www.electronics-tutorials.com/basics/baluns.htm
If you need to run ethernet on one twisted pair, you should use 10base2 (thin coax) equipment with baluns.
http://www.epanorama.net/documents/lan/ethernet_balun.html
Commercial antenna tuners use unbalanced circuits such a Pi-, T-, or L-network to match unbalanced loads to 50 ohms for our transmitters. A simple way to include the capability to handle balanced loads is to include a balun somewhere in the circuit.
http://fermi.la.asu.edu/w9cf/articles/balun/
Using a 1/2 Lambda coax balun. Includes an online calculator.
http://n-lemma.com/calcs/dipole/balun.htm
Balun description and a sample diagram.
http://my.integritynet.com.au/purdic/baluns.htm
A short explanation on how to make your own 9:1 balun for beverage antennas.
http://www.hard-core-dx.com/nordicdx/antenna/feed/9_1balun.html
many examples on blauns built from coaxial cable.
http://www.geocities.com/CapeCanaveral/Lab/5185/circuit2.html#BALUNS