Callcentric is giving away free DID numbers:
Free Phone Number
RESIDENTIAL OR BUSINESS
When you order a Free Phone Number you get a local number in the area of your choice with no setup, monthly or per-minute fees! We offer Free Phone Numbers in parts of New York State that may be used for personal or business purposes. Free Phone Numbers come with 3 inbound channels, and you can add additional incoming channels at any time for free.
You need to make a SIP registration to get the calls forwarded to your VoIP System.