By Pete Karl II, Senior Engineer

There’s no doubt about it. Twitter is a hit. Last year, while MySpace and Facebook were having it out, Twitter achieved a 1,382% year-over-year rate of growth (500K unique users in Feb-08, to more than 7,000,000 in Feb-09). It’s a special and useful product that can achieve that kind of growth.

A gigantic, consistent audience inevitably leads to interest from all parties. Marketers, students, developers, journalists. There are folks with money, with something to say.

Enter developers. Developers in this scenario are facilitators of sorts. Someone will come up with a great idea about how to filter or mash up the conversation on Twitter, and then that someone will call me & my developer friends.

The creators of Twitter created something called an API (Application Programming Interface). An API is what lets computer code use Twitter the same way humans do. Creating Tweets, following people, searching Twitter.com. All of it.

Combine a developer with Twitter’s API (and possibly a paycheck), and your idea can become a reality. Need some inspiration? Here are some examples of great Twitter apps that were built using the Twitter API:

Tweetscan – Get email alerts when your keywords are mentioned on Twitter – http://tweetscan.com/alerts.php
Twitturly – See popular links being passed around Twitter – http://twitturly.com/
Twitpic – Post photos to Twitter (and see photos posted by friends) – http://twitpic.com/
Monitter – Track and visualize keywords on Twitter in your browser – http://monitter.com/

One of the reasons for Twitter’s popularity is that the API has allowed people to access the wealth of its content in the way they find the most interesting, constantly bending and shaping it in creative ways. What will you do with it?