Hello!
At some point in my project, Blender stopped showing these axes on my selected objects. I’m not sure what I did or how to undo it.
Press the button on the 3d view header to turn on the manipulator.
Note that its position is at the current pivot point so if you have set that to be something like the 3d cursor position you won’t see it at the same position as the selected object
See:
http://wiki.blender.org/index.php/Doc:2.6/Manual/3D_interaction/Transform_Control/Manipulators
http://wiki.blender.org/index.php/Doc:2.6/Manual/3D_interaction/Transform_Control/Pivot_Point
Great! Thanks so much!