From NYT (registration required):
A few years ago, a buzz began spreading about Internet telephony, a technology allowing telephone conversations to be made across the Internet rather than exclusively over regular phone lines.
Such calls, made at little or no expense to the caller, were portrayed as a threat to the established phone companies. But the vision exceeded the actual experience, which early users likened to listening through mud.
Now, thanks to providers like Vonage and others, it has found its way into the home. The service is sometimes choppy, but costs are low and quality is satisfactory for routine calls. Moreover, Internet protocol lends itself to inexpensive videoconferencing as well, useful for informal video chats between friends or business associates.