Hundreds of web applications exist today that help you broadcast a message to the world. Some of these also allow visitors to your website to get a customized browsing experience and more easily find what they're looking for. They also help you create a community of people who have similar interests or keep coming back for more. Interaction with and collecting data about visitors to your website are two important features to include, and I've worked a lot with both.
I've also installed and customized learning management systems and virtual classrooms. These are special web applications designed specifically to aid distance learning. As lifelong education moves from brick (buildings) to click (classrooms), the online learning platforms and digital content that these systems are built on become extremely important.