ALT + Left mouse + Drag = Tumble the camera in the viewport
ALT + Middle mouse + Drag = Pan/Track the camera
ALT + Right mouse + Drag = Zoom the camera
SPACE + H = Frame the camera to all objects in the scene
SPACE + Z = Frame the camera on any object that the cursor is over
SPACE + G = Frame the camera on the selected object
SPACE + B = Show perspective views (Top, Front, Right + Perspective)
Hovering over one of the views and pressing SPACE + B again will expand that view