I hereby put the code I wrote into the public domain, yada yada.

A great way to put your code into the public domain would be to put it up somewhere like (ideally exactly like, because they're very awesome) http://github.com/.

If anyone else wants to modify your code the git (and GitHub) workflow is very good - anyone can fork your repository, and if you want to accept their changes that's easy for you to do.

See the GitHub Guides if you're interested.