Often your working on a project and you need a collaboration tool to help keep everyone in the loop. I have had great success with a tool called Basecamp from 37 Signals. It is a very powerful web app that lets you keep track of messages/comments, todos, Milestones, and more. You can start out with the free version which allows you to have only 1 active project. The pricing for the larger packages is pretty good. Once you try it, you'll use it for all of your upcoming projects!