If it's code designed to demonstrate a technique, teach a principle, or show off a solution it goes in a gist. Doesn't matter if it's one file or 30 files. If it's actual code intended to be run, used as is, or forked as boilerplate I put it in a proper repository.
All code will be hosted on GitHub in either private repositories or secret gists. They are separate repo's to ensure they can be sold individually.