United Online, the company behind Juno, Classmates.com and NetZero, has joined the voice-over-IP craze with the launch this week of NetZero Voice. The service offers local and long-distance voice calling over broadband and dialup connections.

While its long distance and computer-to-computer calling will be free, the company will charge anywhere from $3.95 per month to $14.95 after its three month free introductory offer.

Mark Goldston, chairman, president and CEO of United Online, said in a statement that he doesn’t believe people should have to have broadband connectivity to take advantage of Internet calling.

The company is offering both a pay-as-you-go plan through which users can buy pre-paid credits of $5, $10, $25 or $50 or three packaged minute plans.

Using software downloadable from the company’s Web site, users can get the usual features of voice mail, e-mail, instant messaging, Caller ID, call waiting and call blocking. The three paid plans also include a personal telephony number of the area code of their choice, storage up to 2 gigabits, three-way calling and Find Me/Follow Me capabilities.

United Online is already beginning to test the waters of cross-fertilization by joint marketing between NetZero and Classmates.com. Although not on the scale of eBay and Skype, United could use VoIP to make its Classmates product more interactive.