Generally, I release my software under a modified BSD/MIT/X license. As I write this (April 21, 2007), the January 30, 2004 version of the license has the most current wording.
This license applies to software containing either a copy of the license or a reference to it (e.g. "See http://pygmy.utoh.org/license.html" or "Freely available under a modified BSD/MIT/X license, details at ...") or, if I have released the software and no license is mentioned.
Please see the license itself for specifics, but the gist of it is to allow you to use and distribute my software freely for any purpose as long as you maintain my copyright notices and don't blame me if anything goes wrong.