Kall8.com offers $2 a month toll-free numbers with a 5.9 cents per minute call rate. You can even grab a vanity number (1-866-3-CRITIC was free when I last looked) for a few bucks more.
Grab callers when you record you show without giving away your personal phone numbers (calls are forwarded to whatever number you tell them). You don’t need to have the number go anywhere other than direct to voice mail – which is delivered as audio files that you can splice right into your show.
And, bonus, if you’re looking for advertisers – a toll free number makes you look that much more legit.