After finding this link, I was able to set-up free VOIP over wifi/3g with google voice, sipsorcery, sipgate and sipdroid (note: the former 3 are web services, buy a gv account on Ebay for $2, sipgate and sipdroid are free accts to register).
I noticed a few holes in their doc, namely you place calls thru GV (web, not from your Droid!) to your sipgate number, and you'll also need to add your Droid sip credentials to sipsorcery to get calls route to it. I would not recommend abandoning an existing Skype count or other provider as I'm sure a link in this chain eventually breaks (via no longer offering the free service that enables it).
Unlimited Free Calling with Google Voice - Google Docs
As an FYI, my calls over VOIP are crystal clear (but you will need to tweak volume settings in sipdroid), in fact better clarity than over Verizon service from my house.
I noticed a few holes in their doc, namely you place calls thru GV (web, not from your Droid!) to your sipgate number, and you'll also need to add your Droid sip credentials to sipsorcery to get calls route to it. I would not recommend abandoning an existing Skype count or other provider as I'm sure a link in this chain eventually breaks (via no longer offering the free service that enables it).
Unlimited Free Calling with Google Voice - Google Docs
As an FYI, my calls over VOIP are crystal clear (but you will need to tweak volume settings in sipdroid), in fact better clarity than over Verizon service from my house.