On Mon, 27 Apr 2009 19:21:30 -0700, Jonathan Sachs
wrote:

I used to own a house that was built on a stemwall foundation. I
grounded the electric outlets by drilling a hole up through the bottom
plate under each outlet box, pushing ground wires up through the hole,
and fishing them into the box.

I'm now buying a house that is built on a slab, and many of the
outlets are ungrounded. How should I deal with the problem in this
case?

How many appliances require a grounded ( 3 pin ) outlet ?
In my house, that woiuld be the washing machine, and the fridge.
As far as I know, all other plug-ins use a ( 2-pin ) polarized plug.

So, unless your community requires 3-hole sockets, why bother ?
Just be sure that the wide slot is "neutral".