I have Linux Mint 13 running in VirtualBox. How do I suspend it? I just can't find the suspend button anywhere in the menus.
Just close the VirtualBox window. You will be prompted to save the VM state, send shutdown signal to the OS, or power it off.
On the menubar for the Virtualbox window, you will find options to save the state of your system before closing it. Or, on VirtualBox you can usually just close the window and VB will same the state on its own.