During my scrimmage through blogs I visit regularly I came across this little snippet and felt it was worth a share in this thread.
Emergency Exposure DiscThere are many add on gadgets for getting an average white balance, from using a paper coffee filter to the very pricey Expodisc.
Here is another to add to the list, just the top from a cup of Starbucks coffee.
As I usually have a cup or two rolling around in my car, there is usually one I can use in an emergency if I'm out and about

I usually keep a few along with straws in the glove compartment too, never know when they will come in handy for a cup of coffee while travelling.
To use, I set the focus to infinity, place the cap over, then set the custom WB. I dont even need to hold it as it fits nicely inside my lens hood, but that is just a lucky coincidence.
Just something cute I thought I would post.