When I release and publish code, I typically make it Free Software by copyrighting it and applying a license (usually GNU GPL). In cases of smaller code bases or scripts I write, I don't bother to license them. They are generally used as small tools or code snippets.
One choice is to release it as Public Domain. Being in the public domain is not a license. It means the material is not copyrighted and no license is needed. However, I want to retain copyrights but allow others the freedom to do anything. This is based on trust of the author, not a license or an any official law speak.
To make the point clear that I don't care, I adapted Woody Guthrie's Copyright notice to apply to my software.
My new Copyright Notice for unlicensed code:
Copyright (c) 2008, Corey Goldberg (corey@goldb.org) "This code is Copyrighted, and anybody caught usin' it without my permission, will be mighty good friends of mine, cause I don't give a dern. Run it. Study it. Modify it. Improve it. Distribute it. Yodel it. I wrote it, that's all I wanted to do."
Feel free to use this notice on any software you publish, cause I don't give a dern.
Copyright © 2006-2008 Corey Goldberg
Disclaimer The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.