I've stopped playing World of WarCraft but I still find it cool that they give you the option to modify the GUI in numberous and powerful ways. Here is the set-up I was using. As you can see, th HUD disappears when it isn't needed.
If you have a custom interface, take a screenshot and post it. If you have any questions about what was used to make this custom interface or how certain tasks would be completed in it, feel free to ask.