Many developers, myself included, have come to the realization that the traditional coding interview - with whiteboards and coding challenges - is a poor measure of a person's ability to work in the field. It is a high pressure situation, usually designed to make you fail, so they can measure how you work through the problem. In reality, most developers handle these problems by googling it, or searching Stack Overflow.
Instead of waiting for an interviewer to give me a puzzle, and try to solve it on the spot, I have taken the liberty of starting a project and solving the most common problems on my own. All code written here is original, but most of it was supported by google searches, and took several refactors to get it perfect. This is much more in line with the actual job, and still shows what I am capable of, given the resources that every develper expects to have.