I looked into making a recipe site for my girlfriend from scratch a few years ago (I'm well aware I could've used an off-the-shelf Wordpress plugin or similar, but I wanted to learn) and I was surprised to find that there's no real consensus on recipe formats. I dream of a universal format that would allow you to take any recipe and convert between unit systems, and change the portion sizes at will. I suspect one of the reasons for the lack of adoption of such a standard is that copyright law (at least in Australia), makes this impractical. Cooklang looks interesting, but it has the same problem as a physical lined cookbook - I have to rewrite the recipes myself instead of being able to simply copy and convert.