Twitter is now here on the DS. You can keep all of your friends apprised of what is going on around you or in your head. The program is in Spanish and you need to have a memory card to load the program on, but if you use or are interested in twitter the install should be a walk in the park.
If you are not familiar with Twitter, It is a web application that allows you to type very quick messages about what you are thinking, doing, or whatever you would like to says. You can follow people and interact with a huge network of people. It is a great way to keep tabs on someone you care to know more about or just care to watch.