Does anyone have experience with VOIP applications for Android? iSkoot for Skype is sort of a VOIP app but the calls you make with it are routed over the voice network and use your plan minutes.
I just read about Sipdroid for the first time here sipdroid - Project Hosting on SIP/VoIP client for Android.
It looks like this app will let you make calls on WIFI and 3G. I will definitely be checking this out, although I highly doubt Verizon would let something like this run on one of their phones.