Sometimes, for small pieces of code, I use a special license header that goes like this:
/* Released as public domain, or licensed under
* either CC0 or the MIT/X11, whichever gives
* you the most rights in your legislation.
Now, there's a few things in here:
- For many countries, the public domain clause will suffice
- In those where it doesn't the CC0 license will ensure that "public domain"-like rights are granted
- The MIT license is useless, but it's there to give those people who don't know about CC0 an idea of what they get