White Balance Issues

[chaos2k]

I've used snow to WB before and it worked fine.. just dont use yellow snow 

[deedle]

LOL brain. thanks, I should carry a white card in my camera bag.

[sbsbennett]

Don't eat the yellow snow, either! 

[erejotaon2]

 i shoot through the Expoimaging ExpoDisc when i remember to bring it.

...and for those that carry a Gary Fong diffuser, the cloud dome works well. 
simply shoot through the dome at the subject, in manual focus, and you will get a mixture of the surrounding light with your flash (if used).
simply use that image for your custom WB reference. Gary has a short clip explaining it on his website.

[mbonin83]

I usually just set my 7D to Custom White Balance and fix it in Camera Raw, I never shoot in JPEG.  I also have an expodisc, but rarely use it, there is really no need to since your white balance is so fickle.