If you're thinking of switching to VoIP, investigate these services:
Vonage: One of the oldest and most popular VoIP providers. A residential customer can get unlimited access for $24.95 per month. Or, you can get a 500-minute plan for $14.95 per month. See http://www.vonage.com.
AT&T CallVantage: The basic plan for residential customers, with unlimited long distance, costs $29.95 per month. See http://www.usa.att.com/callvantage.
Cablevision Optimum Voice: The Cablevision Optimum Voice plan costs $34.95 per month. See http://www.optimumvoice.com.
Verizon VoiceWing: The basic unlimited service plan is $29.95 per month. Like Vonage, Verizon offers a 500-minute plan for $14.95 per month. See http://www.voicewing.com.