I've written a lot about donating your art.
It's always good to donate your talents to a cause you believe in–whether it's donating your art, your organizational skills, your time, or whatever.
When you donate your art, make sure you get credit! My assistant, Shari Cornish, donated a design to her Vermont NPR station to use on a mug. She got her name and credit on the mug and on the Web site. So many people forget to give credit. It's usually not malicious, but just an oversight due to being overworked and underpaid.