There’s just one problem: Texting 8 or 12 friends at a time can get tedious. That’s where social-networking web services come in: All you have to do is send a text message to the service, instead of texting a dozen people at a time.

The newest SMS social-networking service is twttr, and it comes from the people who created Blogger and Odeo. With twttr, you send status messages to a central location via SMS, and your friends (or optionally, the whole world) can check the twttr timeline and see what you’re up to.

UPDATED: twttr is now known as Twitter, of course, and it’s the hottest social-networking service since Facebook. We’ll have more tips about using Twitter via SMS here soon: Check out our tips on using Twitter with SMS text messaging.

To sign up for twttr, go to www.twttr.com and enter your cell phone number. Twttr will send a “key” code to your phone. Once you enter that code, and pick a username and password, you’ll have an account on Twttr. To let people know what you’re up to, just send a text message to the twttr short code: 40404.

For example, suppose you’re just about to go to the local sushi bar for dinner: Create a text message that says “I’m eating at Kaimuki” and send it to 40404. Off it goes, and in a few moments your status appears on the twttr timeline saying “eating dinner at Kaimuki.”

You can also update your status by entering a message on the twttr web site, which is easier if you happen to be sitting at a computer.

To find out what other people are doing, check the twttr public timeline or send twttr an info request via SMS. For example, to add your friend Karen to the list of people you’re friends with, send twttr this message:

add 415-555-1212 karen

(using your friend’s actual phone number, of course!). If she’s not already a twttr member, she’ll get an invitation to join.

After you’ve added your friend and she’s joined twttr, you can find what she’s up to by sending this text message to the twttr number, 40404:

get karen

You’ll get a text message back with the latest status update that Karen sent to the system. Simple!

Here’s a list of Twitter mobile commands that explains other commands you can send to the system via text messaging. So far there are not a lot of commands, and not a lot of people using twttr. But if you play around with it, you might find it’s a handy way to keep in touch with people or to have fun with SMS texting.

I’ll be experimenting with twttr a bit, and I’ll update this entry with more information as I discover it. I’d love to hear what you think about it, too.