With a simple interface, Twit2Tel offers a service that can not only get you in touch with your Twitter buddies, but also increase your stalker status in the process. The site claims to let you make a four minute phone call to any other Twitter user for free.
All you have to do is provide them with your phone number and let their application connect with your Twitter account and you can start making phone calls. There doesn't seem to be any real restriction on which accounts you can call, so feel free to start dialing up all those celebrities that you're following.
The site works by calling you, then connecting you to the phone number associated with the Twitter account you wish to get in touch with. I called @kimkardashian just to see if it would go through, and was only allowed to leave a brief voicemail (sigh). So, don't expect to start getting in touch with famous people unless they have their own personal phone number attached to their account. However, you will be able to leave a voicemail for them, and you will have very little trouble getting in touch with anyone you actually know on Twitter who has their cell phone updates enabled.
The service provided by Twit2Tel is actually very useful, especially if you don't know the phone number of the person you're wishing to dial. While we can sit and joke about calling celebrities, the bigger value in this service is getting in touch with friends you have on Twitter, and no where else. Go make a phone call, and let us know what you think of Twit2Tel in the comments.