According to w_tom :

Second, install a Ground Fault Circuit Interrupter Duplex
Receptacle:
http://www.homedepot.com/prel80/HDUS...D=9876&pos=n04
Electrical code specifically lists the second solution -
which is also a safer solution. A sticky label, also required
by code, is provided warning that ground does not exist.
Attach label to GFI faceplate.

Once you install a GFCI outlet on a groundless circuit, you _are_
permitted to install/replace with ordinary three prong outlets
downstream of it (the GFCI itself is three prong obviously ;-),
provided:

a) you label them as GFCI-protected without ground
(stickers come with GFCIs for that purpose)
b) do not interconnect the grounds on any of the outlets.

I would not install a ground strap from a 3 wire outlet to the box:

a) it's pointless in most cases (often already accomplished by strap of
outlet on a metal box.)

b) May increase risk of ground wire interconnect in multiple outlets
(see (b) above) (ie: cable armor).

The ground prong in a groundless circuit is _supposed_ to be completely
un-connected. Half-measures make it more dangerous, not less.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.