Here are links to specific portals for students:
Paid Summer 2012 Undergrad Research Placements:
Over 800 programs – REU and other summer research opportunities for undergrads
Bridge to the Doctorate, IGERT and NSF Grad Research Fellowship programs provide generous stipend and tuition support for students through the National Science Foundation:
Finally, here is a link to a flyer (pdf) which can be printed to post if you so choose.