how do these work? could you give me links so i can look em up on b&h or adorama?
eh, they won't really tell you how they work. If you go here, you can read up all about it.
http://photography-on-the.net/forum/forumdisplay.php?f=35
If you want a more specific thread, read this. I made a post about what you need to go ocf.
http://photography-on-the.net/forum/showthread.php?t=730719
----------------------
What you need to go ocf, really depends on your. If you want to retain ETTL then you'll need some PW mini's or any other trigger with ETTL capabilities. It can get pricey. However, the alternative to those triggers, would be getting a cord such as this:
http://flashzebra.com/ttlcords/index.shtml
You retain ETTL and it's a lot cheaper, but it's not wireless. You have to have it connected to your camera.
----------------------
If you don't care for ETTL then you can invest in less expensive triggers. There are a bunch out there such as Yongnuo, Cactus, or my personal favorite and weapon of choice, CyberSyncs. With these triggers, you'll have to be firing the flash with manual settings. (It'll get you to practice and perfect the flash as opposed to using ETTL where the flash does the work for you)
The trigger is mounted to your camera's hot shoe and the receivers are connected to however many flashes you want to be fired.
---------------------
Assuming you're picking up some flashes and not monolights, you can pick this kit up:
http://www.bhphotovideo.com/c/product/425220-REG/Impact_DFUMK_Digital_Flash_Umbrella_Mount.html
If you get anything Speedlite that's not a 580EXII, you'll need this in conjunction with the kit:
http://flashzebra.com/products/0128/index.shtml
---------------------
Another option is to buy two Speedlites; one 580EXII and another such as the 430EXII. Your 580 would be mounted on your camera and the 430 would be your slave. When set to its proper settings, the 580 will fire the 430 assuming that it's in line of sight. Indoors, this would be fine, but outdoors on a bright sunny day, the sun may present some problems.
Rather then buying two flashes, you can just buy one flash and a ST-E2. Essentially, it's a trigger that's mounted on the camera.
---------------------
Just use the links that I shows you at the beginning of this post and you should be fine. All the information you need is there. Good luck