I was writing up a new blog post that had some Yaml config files in them. I've been using the Syntaxhighlighter Evolved plugin for this, which has worked remarkably well. Unfortunately it seems that Yaml is not one of the supported languages, and I couldn't find much about it.
Luckily for me the author wrote a fantastic blog post about extending his plugin, which I used to create my very first WordPress plugin. If you're looking to add Yaml highlighting to your blog you can grab my SyntaxHighlighter Evolved: Yaml Brush plugin right off of the WordPress Plugin Directory. The first version is pretty simple, but I'm considering collecting a few different languages together for a more comprehensive pack.