580 Off Camera Light

I have two 580 flashes and am wondering if there is a way that I can set them up to use them off camera on stands with umbrellas. I am not very knowledgeable in this area, and would really apreciate some help. What would I all need to buy, I already have the 580's. I will only be using them inside to light family photos and such incase it rains on the day of a wedding. Also how big of a group would I be able to light with them. Thanks for your help, if there is already information about this on the board somewhere I would appreciate being pointed in that direction.
Thanks,
Lally

If you want to use both of your 580EX's off camera, you will need to buy another 580EX (I am not a fan of the ST-E2). But you can have a lot of fun using one on-camera 580EX as a Master and one off-camera 580EX as a Slave.

What would I all need to get them to work with one off camera, and one on camera? Does anyone have any photos of lighting a group with one flash on the camera, and one off the camera? What settings do I put my camera and the flashes at?
Thanks again

Set the on-camera flash to Master and set the off-camera flash to Slave.

You should also peruse the manual as it has some excellent examples of this technique.

There are many good stickes at the top of this forum, I would suggest you read through them.
There are at least three ways to do what you want. First is the Canon ST E2. Some folks don't like it, but I find it works rather well especially indoors. It allows you to control your other speedlight in groups and still maintain ETTL metering.
Second would be to buy another 580 or even 550, then use a 580 as a non-firing master. Pretty much the same as the ST E2 but alot more expensive.
The third and way would be to use radio transmitters such as Pocket Wizards or the cheap ebay ripoffs from China. These will work fine but you do loose ETTL and will have to run the speedlights in manual mode.
I use the ST E2 with 3 speedlights in different groups. The 580's can be used with umbrellas or with the stand that comes with them. I will place them behind chairs and in far corners to light a large room. I have never had a problem with my ST E2.
Check out Stobist.com for more help with lighting.

Lally. Lots of good info around here. But, one of the nicest hands-on Canon 2 or 3 flash set up sites, with photos, is that fellow Chuck Gardener's tutorials here: http://super.nova.org/​DPR/#Canon

Jack