By default, ortho toggles on and off with the shift key. Dont forget to set your ortho to your preferred angle (90 is default, you can set it at 15, 30, 45, etc.)
Hotkeys can be custom programmed in rhino options. Tools_Options, and then go to aliases. Click the help button. An example of one of my custom aliases is as follows. AS = '_Invert Hide. I simply select one object, type AS, and hit enter. Selection is inverted, then hidden. Unlimited hotkeys are available.