After four or so years of using wordpress.com for my blog I finally figured out how to highlight code (prettify) in a blog post.
A thank you to @jasonclevine who sent me message on twitter on how to do this.
All you need to do is wrap your code with
There are a bunch of different languages supported and other options which can be defined. You can find all the details here: http://en.support.wordpress.com/code/posting-source-code/