Yeah, it's a bit nerdy, but twitter is growing in popularity each day. Being a bit of a nerd myself, I signed up for an account years ago, before it became popular. Of course, since not many people were on it, I stopped using it pretty quickly.
These days however, it is full of celebrities, brands, publications, and regular people like us. Plus, now that most phones are "smart" phones, posting stuff to Facebook or Twitter has become as easy as sending a text message.
1) Stay In Touch With Friends
This one is fairly obvious, but if you have friends on twitter it is a good way to keep tabs on what they are up to. If they use a location based service like foursquare, you might even be able to keep track of where they are. Useful or creepy? You make the call, I'm not judging.
2) Become A Twitter Celeb
If you're funny or have interesting stuff to say, you'll likely gain followers quickly. This can be a good ego stroking. Also, depending on your profession, twitter can be a great way to promote yourself and engage with people.
3) Meet Normal Women
More women than you'd think are on twitter. The fashion and publishing worlds are HUGE on twitter, and comprised primarily (not entirely) of women. I'm not inviting you to be a sleazeball... but in the process of regular banter, you might be surprised who you might meet. If this is a route you'd like to go, fill your short twitter profile with honest info about yourself and use a flattering photo.
4) Funny Content
Many comedians and actors are on twitter. Most post funny content or links; some even personally respond to you.
5) Adult Content
Depending on your sensibilities and relationship status, there is a lot of adult content to be had on twitter. From adult film stars who maintain their own accounts, to regular people who are quite... umm... open, shall we say.