To any campus groups planning to participate in National Ask An Atheist Day on Wednesday, April 13th, the students at the Illini Secular Student Alliance (at the University of Illinois) have a couple additional resources you can use:
There’s this poster:

You can download a generic version of the poster (PDF), or use this Adobe Illustrator file to add your group’s name/logo.
There’s also a sample press release you can use as a template to let local media know what you’re doing.
If you have anything else to add to the growing list of resources, please let us know in the comments!
(Thanks to Becca for the link!)