The Creative Commons has released CC0 1.0 Universal, the "no rights reserved" license.
Here's an excerpt from the CC0 FAQ:
Are CC0 and CC's Public Domain Dedication and Certification ("PDDC") the same?
No. PDDC was intended to serve two purposes—to allow copyright holders to "dedicate" a work to the public domain, and to allow people to "certify" a work as being in the public domain. Our experience with PDDC shows that having a single tool performing both of these functions can be confusing.
CC0 is a single purpose tool, designed to take on the dedication function PDDC has been performing, but in a more complete and legally robust way. CC0 is universal in its applicability, intended for use world-wide by anyone anywhere holding copyright or database interests in a work. PDDC is based on U.S. law, and the enforceability of its dedication function outside of the U.S. is not certain.
Read more about it at "CC0: Waiving Copyrights" and "Want to Waive Copyright? Creative Commons Has a Tool for You."