I would suggest you release the code under an open source license instead of the public domain. A BSD-like license grants others the right to modify and distribute the code, protects your liability, and removes the uncertainty about whether something is in the public domain.
Lots of software that says it is in the public domain does not do a proper delegation and exists in a legal gray area.
If you really want to dedicate it to the public domain, check out Creative Commons. They have a dedication you can use.
