Finally, here's a Web 2.0 app that I like today: Vitalist. It's a to-do list manager. Yawn, you say? Not so fast. With such a simple concept, the story is purely in the implementation. And Vitalist does it right. It's simple to use, and it's fast. Most features are blindingly obvious. And it has a lightweight version for accessing your list from your mobile phone instead of your computer.
What makes Vitalist work are the different ways you can organize tasks. Discrete items you need to get done are just entered as tasks. You can also associate tasks with projects, to group them together. And you can associate tasks with "contexts," such as "phone," or "home office," so when you sit down in one of these contexts, you can see all the items that you can get done there. You can drag tasks to projects and to contexts in some views, which is a neat trick for a Web service. You cannot, unfortunately, do so from the overview "dashboard" screen that shows you a list of all of your tasks.
The basic package is free. Paid versions add security and collaboration features. And yes, you could force Outlook to do everything Vitalist does. But it wouldn't be pretty.
Like the famous Franklin Covey system, Vitalist is based on an overall school of time management, in this case the Getting Things Done or "GTD" scheme, which is very big among techies right now. (See 43Folders.) It's a solid system, and if it makes sense to you, you'll probably find Vitalist a useful Web-based implementation of it.