I purchased an OOMA (http://www.ooma.com) VOIP hub last week. This device allows you to make phone calls via VIOP with a one-time hardware purchase and without additional monthly connection fees
I spent 10-20 minutes to register my new number (I could have transferred my current number for a small fee, but decided on a new number instead) and set-up the hardware thru my Clearwire internet receiver. Since it's possible to choose a number anywhere in the US (I believe the service is also available internationally), I could have easily chosen a primary number in Boston so that friends/family there could place a local call to me, and then have my secondary number local to here in Seattle for friends and family here
Three hours of calls later, I'm well pleased with the sound quality even while simultaneously downloading significant data files or streaming videos from YouTube.
The hub runs roughly $200US, and with the exception of a yearly $11.99 FCC tax (maybe only applies to US customers) there's nothing more to pay ever if you utilize their basic service. For an additional $11.99US monthly you can upgrade to their Premier service which includes the ability to have a second dedicated phone number, call forwarding, multi-ringing (simultaneously ring your land line and cell), and voice mail services
As an added benefit, it's even possible to listen to your voice mail via a secure log-in web browser
all the best,
R