A quick look also has a jiffy = 1 cm / speed of light and 1 Planck Length/speed of light. Never heard of a shake.
According to this:
[link|http://www.unc.edu/~rowlett/units/dictS.html|http://www.unc.edu/~.../units/dictS.html]
..a shake is 10 nanoseconds, about 10 feet.