While it's quite easy to connect a PHP application to Twitter (I've discussed it in detail in this Devzone article), there exist a number of other free micro-blogging sites that also expose open APIs. In this article, I'll introduce you to Plurk, which includes a JSON-based service API and also comes with a PHP library to simplify integration with Web applications.

He includes sample code showing how to connect to their API (with the help of the php-plurk-api) and work with the results. He shows how to search the service, get the latest "plurks", find the entries for a given user and create a simple form for uploading comments to your own Plurk account.