Address Book Continued is a multi-user address book Web application. It also makes use of AJAX, which means that page reloads only happen on login/logout; the rest of the operations is handled asynchronously in the background. It's well usable, even over slow connections. You can even install ABC on your desktop PC and configure it so that it doesn't require login for connections coming from the local computer.
AntFlow builds upon Apache Ant to provide a new approach to simplifying system automation that uses pipelines of hot folders chained together to perform a given task. Using XML, it associates an automated task such as data transfer, encryption, or XML processing with a directory on the local system. Whenever a file is copied or written into the hot folder, the associated task is executed and the file is moved to the next hot folder in the pipeline for further processing.
Checky is a document validation and analysis extension for Firefox, Mozilla, and Netscape. It provides an easy-to-use interface to many free and commercial online validation and analysis services. It allows the user to validate, analyze, view, and inspect documents containing HTML, XHTML, CSS, RDF, RSS, XML, P3P, hyperlinks, metadata, and many more. It can check Section 508 and WAI compliance of documents with many helpful services. It can help in the design, development, and maintenance of accessible documents for a semantic web.
CookiePie is a Firefox extension enabling you to maintain different cookies storage in different tabs and windows. You can open multiple Gmail/Yahoo Mail accounts in different tabs and windows simultaneously. Developers can use CookiePie to test their Web software with different application users without the need to open different browsers.