Note: This document is work-in-progress. Please don’t publish it on news sites, or otherwise link to it in public without the author’s permission. Private linking is acceptable.
It is not wise to license one’s code under the Public Domain because the Public Domain is not widely understood or accepted internationally, and because licensing code under the Public Domain may not be possible. Rick Moen gives more reasons under “Public Domain” in the Licensing and Law section of his knowledge base.
If you’re interested in making your software as-close-to-Public-Domain-as-possible, you should choose the MIT/Expat License or a similar licence such as the ISC licence.