Go ape! It's Darwin Day!
And the Center for Inquiry provides a short list of resources for campus organizations or anyone else who wants to sponsor an event. In particular, you may contact their speakers bureau to find speakers on evolution, creationism, and intelligent-design creationism (it is a complete mystery why hardly anyone from Panda’s Thumb is on that list, but we will not go into that now). Additionally, Center for Inquiry directs you to the International Darwin Day Foundation, where you may find a list of activities near you, and, of course, the National Center for Science Education.
CFI recommends that you try to teach someone about evolution or other scientific principles and notes that the Public Broadcasting System has a wealth of material on evolution, science, and Darwin. The Understanding Evolution Web page is likewise an excellent resource.