V.O.I.P. is all the craze these days. You can't turn on the TV without seeing a Vonage commercial. V.O.I.P. stands for "Voice Over Internet Protocol", or simply, it's talkin through the puter.  Instead of sending your calls over those copper phone lines, your calls go out over whatever internet connection you happen to have. There are two ways to use VOIP, on your computer or with a regular phone.
    Programs that let you talk over your internet connection have been around for some time. I remember using them way back in 96 (is that right Travis?). If you use MSN messanger or GoogleTalk all you need is a microphone and speakers and you can talk to anyone on your buddy list. The most popular program for calling people from your computer is called Skype. With it, you can call for free anybody else who is signed up. The best part, is that for a small fee, you can call any real phone number. I use skype to conference call with my coworkers in San Diego.
    There are other companies that allow you to use a regular phone, have a regular phone number, but use your internet connection to make calls. Vonage is the most popular but there are a few other good ones out there. Other companies like Comcast and Quest call in "Digital Voice" in a shameless attempt to trick people into thinking it's something else. They charge TWICE as much for the EXACT same thing. DO NOT buy VOIP from Comcast or Qwest under any circumstances, it is a huge rip off.

The Good
    You can save a lot of money over traditional telephone companies. For $25 you can get unlimited minutes and free long distance (Canada too!). They also include lots of other features like call waiting, caller id and voice mail for free. International calls are also pretty cheap.
The Bad
You have to have a good internet connection already. Really you should have cable for it because if you have DSL then you are probably getting it from you phone company at a discount because you use their phone service. So switching to VOIP would nullify that advantage.  Also, if your internet goes down, you can't use your phone either.  Once a month or so we'll have a call get dropped or garbled too.

We've been using VOIP for a year and a half and I highly recommend it. If you have been thinking about getting cable internet it can help defray that cost. If you do decide to switch then find someone who is using it and have them refer you. Both of you will get a good discount.