This is my VOIP setup:
Free pbxes.org account, connected with 2 outbound and 2 inbound trunks. outbound: whistlephone (
www.whistlephone.com) for free calling to the USA, voicebuy (
Quality Wholesale VoIP Termination | Voicebuy VoIP Provider) for super cheap calling worldwide (wholesale rates*); inbound: callcentric (
Callcentric - VoIP Internet phone service) which also serves as outbound backup, and inbound from anveo (
Anveo - The Smart Way To Use Your Phones) - really cheap DID's worldwide (like 1 buck per month), many with fax and sms support.
All connected to a two line PAP2 adapter and then to a two-line AT&T phone.
* There are cheaper wholesale services, such as voxbeam -
Voxbeam: Wholesale A-Z VoIP Termination but they work based on IP authentication rather than SIP username/password. The rate difference is maybe 2-5% on average so for me it's not worth the rick of SIP authentication by IP address.
Another good wholesale service with great rates is sonovoip -
Quality Wholesale VoIP Termination | SonoVoIP Wholesale VoIP Provider - but they also have only IP address authentication, and no SIP username/password.
Wholesale rates - we are talking rates like Germany 0.9 cents/min, UK 0.7 cents/min, Dominican rep. Fixed 2.3 cents/min, Colombia Medellin 1.3 cents/min (for AZB

), everything billed in 1/1 increment (1 second initial, 1 second increment). All these companies accept as low as US$25 recharge, usually by Paypal or Moneybookers. This is really a great option for cheap calling worldwide.
If you need inexpensive Dominican Rep. inbound DID with 100 minutes of local outbound calling to DR landlines (Santo Domingo, Santiago), prepaid, month by month basis, this is your best bet: Wind Telecom -
http://wind.com.do/telefono/planestelefono/voz-local plan Voz Local 100. it's RD$125 + taxes = US$4.2, unbeatable offer, cheapest DR DID you can find anywhere.