While I love coding with my editor in fullscreen mode, I also enjoy having apps such as Campfire or Rdio accessible on another monitor. One complaint I have had with the default OSX fullscreen mode is that it causes a second monitor to show nothing but the grey textured spaced background. I was thrilled the other day when I discovered a feature in Sublime that allowed me to use a "simple" fullscreen mode which behaves differently than the standard OSX mode. If you add the following to your Sublime preferences:
Using the Enter Full Screen shortcut will allow you to have nothing but your code on one monitor and still use your second monitor for whatever apps your heart desires. Simple preference edit that has made my work flow that much better.