Jupiter is the common name for the MIT Lab for Computer Science Weather Information System. It is an automated interface which utilizes voice recognition and text-to-speech technology in providing an interactive method of getting weather forecasts. You can ask Jupiter about temperature, wind speed, humidity, sunrise/sunset times, and advisories, and it will respond with the relevant data. It knows about 500+ cities worldwide, most of those being in the United States. Jupiter remembers queries, so you can say something like "Will it rain tomorrow in Boston?" and subsequently ask, "What about Paris?" The system reportedly has 89% word recognition for new users, and 98% for experienced ones, which is an excellent success rate - especially considering the amount of sound quality lost over the phone line.
The toll-free number for calling Jupiter is 1-888-573-TALK (1-888-573-8255). If you wish to call Jupiter from outside North America, the number is 617-258-0300. This is not a toll free number, and you will be responsible for the (international) long-distance charges.
For more information about Jupiter, visit http://www.sls.lcs.mit.edu/sls/whatwedo/applications/jupiter.html.