Hamburger Resource #1
This website gave some good examples and tutorials for building hamburger menu's using only CSS and HTML. I felt it added enough detail and showed the examples well that it was an easy to follow along with website. It provided the code for the eamples they used.
Hamburger Resource #2
This website continued to show examples and the coding involved to make the menu's. They did take it a step further and used jQuery into the menu building. This opens up more possibilities for setting up how the menus will react and behave.
Hamburger Resource #3
This website was really interesting. Right away they take you into a big collection of transitions that can be used for the hamburger menu. Some of the differences were very subtle, although there was big changes behind the scenes to make each happen as they did.
Summary
There are many ways that you can style and manipulate menu's. The hamburger style using just HTML and CSS are only the start.