Is there a way to make free/low-cost international calls between two non-smartphones?

I’m going to be in Singapore for awhile and want to know if there’s a way to make calls/send texts to the US that is:

a) free/almost free
b) between phones, not phone-PC, iPod-PC or PC-PC
c) between two non-3G phones

Both parties have Google Voice accounts.

Any tips? Thanks!