As you'll quickly find out when you start shopping around for Voice-over IP service, there's no shortage of providers; in fact, the supply is in danger of becoming a glut, a condition that might benefit you if you're a conscientious shopper. We're here to help you get started with this list of providers, their locations and Web sites, and a note about what makes each one special (we'll leave the price-comparison chores to you, since provider rates are subject to rapid change). By no means is this list comprehensive; we avoided companies that cater to resellers or that specialize in phone hardware or VoIP gateways. That eliminates, for this discussion anyway, such big players as Cisco, Siemens, and Nortel. Rather, these are direct-to-consumer Internet telephony service providers. So if you don't see anything you like here, exercise your right as a red-blooded American consumer: Shop around.

8x8, Santa Clara, Calif.

8x8, under its Packet 8 subsidiary, loves to tout its videophone service for $29.95/mo.; it also offers enhanced 911 (E911) service, which automatically routes calls and computer-based "screen pops" of caller information to local emergency personnel.

AccessLine, Bellevue, Wash.

Thanks to its onsite VoIP network, AccessLine says it can save companies the cost of upgrading or replacing its phone hardware; it also offers E911.

AltiGen, Germantown, Wis.

AltiGen's IP telephony systems are software-based, a feature the company says makes it simple for the end-user to make changes and upgrades to the system.

AT&T, New York City AT&T's CallVantage program promises consistent voice quality, and offers unlimited calling anywhere in the U.S. or Canada; the company also has a number of scalable VoIP plans for businesses.

Avaya, Basking Ridge, N.J.

Avaya says its specialty is the ability to cater to virtually any-size business. Its IP Office--Small Office Edition is designed especially for companies or remote locations with no more than 28 users.

BroadVoice, Lowell, Mass. BroadVoice's claim to fame is single-rate unlimited international VoIP service. Plus, according to the company Web site, Aerosmith's Steven Tyler is a subscriber.

Broadvox Direct, Cleveland Broadvox Direct's Unlimited calling offers two telephone numbers for the price of one-one for you, and one for a friend or family member, for whom all calls to you are free.

Comcast, Philadelphia

A relative newcomer to IP telephony, Comcast recently launched its VoIP service in three markets (Philadelphia, Indianapolis, and Springfield, Mass.) with an eye on a 20-market roll-out by the end of 2005. When that happens, look for the cable giant to muscle its way into the market with authority.

Covad, Santa Clara, Calif.

As one of the big daddies in IP telephony, Covad's selling point is its size, reach, and stability. Its specialty is VoIP bundled with high-speed Internet service.

Lingo, McLean, Va.

Lingo's strength is in simplicity. The company offers a one-price business plan with unlimited service to the United States, Canada, and Western Europe. And, they throw in a free month of service.

Mitel, Ottawa, Canada

In a "preferred partnership" arrangement, Mitel's VoIP services run on HP hardware, which should lend Mitel some muscle in refinding its services and garnering subscribers.

Onvoy, Minneapolis, Minn.

Onvoy is standing out by providing both direct-to-consumer and wholesale VoIP services, the latter via its Bandwagon program. The company offers a wide variety of VoIP packages for business, too, with a notable presence in healthcare.

Pingtel, Boston

While most VoIP systems are proprietary, Pingtel's SIPxchange suite gives small-to-medium-sized businesses control over when and how to deploy their VoIP technologies. Pingtel says it's the industry's only open-source SIP-based Internet protocol PBX (private branch exchange).

Skype, Luxembourg

Peer-to-peer telephony provider Skype has made a name for itself as the free VoIP with just one tiny catch: The folks you make those free calls to have to by Skype subscribers too. That hitch aside, Skype's regular service (which it touts as "not free, but pretty cheap") has been attracting converts too.

Sound Choice Communications, St. Paul, Minn.

A relatively new player in Internet telephony, Sound Choice is among the new breed of VoIP providers who are hungry enough to make up in customer service what they lack in experience. Sound Choice's service is currently available only in the Midwest.

SunRocket, Vienna, Va.

If your business does some big-time volume calling, a provider like SunRocket might be worth looking into. The company is gaining a reputation for rock-bottom pricing, and offers flat-rate calling plans that offer unlimited calling for one annual fee.

Verizon VoiceWing, New York

Pro: The stability, reach, and muscle of a telecom giant. Con: No E911.

Voiceglo, Ft. Lauderdale, Fla.

Voiceglo is making waves by offering VoIP service exclusively via its proprietary GloPhone. The strategy must be working, because the company claims average monthly user growth rate of 122 percent, with a presence in more than 60 countries.

Voicepulse, Jamesburg, N.J.

As much as perhaps any VoIP provider, Voicepulse takes pains to ensure that its service is literally plug-and-play. When you purchase the company's service plan and adapter, all cables and connectors are included, as is the an international multi-voltage power supply, which jet-setters should love.

Vonage, Edison, N.J.

As one of the first and best broadband phone companies, Vonage has a leg up on a lot of its competitors. As a result, it can throw in for free features (like call forwarding, call waiting, voicemail, three-way calling, call return, and caller ID block) that other providers charge extra for.