Google is your friend, IF you don't mind putting your stuff into the cloud. I keep my calendars, contacts and files and to-do lists, Having an Android phone makes all that information available on the go, too.
Another tool I might recommend is the Personal Brain (www.thebrain.com), which is available as a free download. It is a mind-mapping application that allows you to relate anything you enter to anything else, in a visual format. I find it very useful for keeping track of interrelated tasks with lots of "moving parts" and pieces of information.