Back when the first rounds of web applications took off in the late '90s and early '00s, I was either in grad school or working in the non-profit/political world. I wasn't following the details of how early online tools like Blogger grew in popularity, so I'm unsure if the tremendous number of third-party tools and applications that are developing around Twitter is normal. But almost every day these days I seem to come across a new way that developers are extending the micropublishing service, either refining the core product or pushing it to do new things. I don't know if that has happened to the same extent with other apps in the past, but it is a demonstration of how at Twitter has some quite long coattails.

Twitter provides an API that opens up their app to some level of granularity. For example, after some initial tweaking, outside developers now have access to direct messaging (accessed by prepending "d [username]" to a tweet). That move created all sorts of ways for inviting Twitter users to engage with people who want to provide them with information or other services. The openness of the Twitter API have been a giant "welcome" banner for anyone wanting to make use of their platform. And made use of it, folks have -- Twitter's Biz Stone has said that the Twitter API gets at least *10 times* the traffic of Twitter.com.

Maybe the key is that Twitter is so simple: just 140 text characters zapped to a centralized server and relayed to whomever users want to receive them. They don't bring so much to the party that no one else thinks they need to bring a thing. The innovation that has been built out of it has been neat -- and instructive -- to watch.

Input Tools. When it comes to the fairly straightforward task of managing input into Twitter, any number of third-party gizmos have popped up. Desktop-based tools like Twitterrific, Twhirl, and Snitter are all engineered to the same end -- conveying your short post to the Twitter service. Where these applications are different is the options that users have to customize the fine details on how they post. Each has a unique look, layout, and feel.

Output Managers. More interesting than input tools are those that help managing Twitter's sometimes overwhelming output. TweetScan, for example, allows you to search Twitter streams and set up something similar to Google Alerts, where you get an email notification when your keywords are mentioned. Quotably sprouted up to correct what seems to be a flaw in Twitter -- responses to posts routinely get lost in the stream of messages, by organizing conversations in threads like how blogging tools like Scoop were built to accomplish. As Twitter doesn't (yet) provide users with traffic stats on their posts, Tweetburner boosts the usefulness of the service by creating custom URLs that can be embedded in tweets and then tracked. And then there's something like TweetPeek, which bundles together feeds to make the service more group friendly.

Extensions. A bevy of third-party tools exist to not just help better manage Twitter, but to grow it into something more than it is right out of the box. Twitsig, for example, takes your Tweet stream and converts it into images that can be used as signature files in forums and email. Foamee is both a protocol for indicating that you owe someone a beer or coffee and a tool for tracking who owes who drinks. But most intriguing to me is something like Qwitter, a program developed by Tobacco Free Florida. Tweet the number of cigarettes you've had in a day to the Qwitter Twitter account, and the service will keep a progress chart of how often you're lighting up. Or you can tweet in a note on your quitting campaign -- "realized tonight that it's hard to not smoke while grilling" -- and Qwitter will compile your thoughts into a journal for future reference. As a public advocacy and policy use of Twitter, that's a useful model to watch.

The powers-that-be at Twitter made the decision to create a robust API, a choice that is providing the oxygen for a thousand flowers to bloom in software development land. And it's not only plug-ins that are being developed; some of these new tools are standing in a partnership relationship to Twitter. The potential is there for many more symbiotic apps to be created, standing separate but dependent -- kinda like the many bail bondsmen who set up shop outside jails. Now the question is whether there is a business model that supports keeping the party going...