I'm an inveterate list maker and I am never happy until I have all my tasks filed away and categorised. As I get older I realise I begin to rely more and more on my reminders and task lists. For new Mac users there's an easy and simple way of keeping track of your tasks built right into iCal. These tasks can be synchronised between computers (for instance by MobileMe) and you can view the lists in Mail. Also, working in Mail, you can create Smart Folders to provide views such as all tasks in a particular calendar or all tasks due today.
If you are a bit more ambitious I would recomment Filemaker Pro's Bento as a way of adding to the rather basic task management capabilities of iCal. The beauty of Bento (apart from the fact that it is a powerful and easy-to-use database in its own right; it's the database for the rest of us) is that it works directly on your iCal tasks data without any need for synchronisation. You can even add fields to your iCal tasks for greater analysis and reporting capabilities. Yet these fields remain in Bento and are not added to the simple items in iCal. Whenever you open Bento they are there.
Bento allows for Smart Groups but with greater customisation of parameters. All in all, it provides a great enhancement and adds great power to the standard iCal offering. I also use Bento for customised databases which are easy to set up–such as an exercise log, a list of books, a packing list. It's really easy to use.
The major drawback of Bento is that there is no iPhone version available. And that's where OmniFocus comes in. It's a very powerful task management system based on the GTD principles of David Allen. GTD is a fascinating concept and needs an item of its own, so watch out for Chapter 2.