Electrical question

Greetings all.  I have a, hopefully, simple electrical question.

Let's suppose I have a properly wired 240v outlet right where I need some 
120v outlets.  I have read that is is possible to put in a pair of 120v 
outlets in place of a 240v.  It's made by using the neutral commonly to 
both duplex outlets, red-hot to one and black-hot to the other, then 
common ground to the box (each duplex is then on a different hot leg).

Is this really possible?  Or did I read something not quite safe?  If it 
is safe, is it a real stretch to make a portable outlet box for the 120v 
and plug it into a 240v outlet, then provide a means of grounding it 
properly (long ground lead attached to the 240v face-plate screw, for 
example).

Thanks in advance,
Chris