One of the hardest things to do sometimes is staying productive and organized. To keep myself on my toes I use [some] of the following programs. Most of the following programs are free, but not all.
Mac OS X

Things (Free Until January 6th)
I myself have used Things quite a bit. Things is the perfect blend between features and simplicity. Things will also support “teams” and you will be able to share tasks with other people. That feature hasn’t been ironed out yet, but Cultured Code has promised it will happen. And if you’re an iPhone user, they have an iPhone version that syncs flawlessly with its desktop counter-part.
Things is currently free, but will cost $49 when it it released on January 6, 2009. But if you subscribe to their newsletter, it will be $39.

Anxiety
If you’re looking for a simple and beautiful to-do list, Anxiety is a great contender. Anxiety integrates with your “calendars” in iCal and sits in your menu bar.
[Anxiety]

CheckOff
Another worthy contender for simply managing your to-do’s is CheckOff. CheckOff is an independent application unlike Anxiety, which is simply a separate interface for the iCal to-do’s. CheckOff does run in your menu bar though.
[CheckOff]

Backboard
Backboard is a simple Mac application that merges Backpack (a simple web-based to-do application) with your desktop.
[Backpack]
Windows
FruitfulTime TaskManager Free Edition
FruitfulTime’s website says the following about FruitFulTime TaskManager.
Basic todo list management tool for Windows available to download for free. Limited features, no support, for private and non-commercial use only.
[FruitfulTime TaskManager Free Edition]
Cross-Platform
Task Coach
Task Coach’s website says the following.
Task Coach is a simple open source to-do manager to manage personal tasks and to-do lists. It grew out of Frank’s frustration that well-known task managers, such as those provided with Outlook or Lotus Notes, do not provide facilities for composite tasks. Often, tasks and other things todo consist of several activities. Task Coach is designed to deal with composite tasks.
Task Coach is for both Windows and Mac OS X.
Slife
Slife’s website says the following.
Slife is a time and activity analytics application for both Mac and Windows that automatically keeps track of where you spend your time on your computer.
How Does Slife Work?
Slife observes as you interact with applications, documents, email and web sites and then displays detailed statistics of your computer usage in a set of intuitive and easy to use visualizations.Why Do I Need Slife?
With Slife, you can finally understand where you are spending your time and energy, and focus on what really matters. Thousands of designers, architects, consultants, developers, and many others use Slife to keep track of time and manage their productivity.
[Slife]
JDarkRoom
For many of us, our attention spans usually can last about 3 minutes at a time until we see a Growl notification telling us we have new articles in our feedreader or MailPlane telling us that we have a new e-mail. This is where JDarkRoom is great. It is simply a full screen text editor to block out all distractions.







Come here from your Tweet, I am using PC and really like Fruitful time.
I notice you don’t include Sunbird or Lighting add-on for Thunderbird here. It’s a quite useful calender and task manager for both PC and Mac user.
Task2Gather (http://Task2Gather.com) is one of the great collaborative tool for iPhone. It allows for online collaboration via iPhone, browsers on desktop, and Windows Mobile.
Task Coach seems to be more effective and of my needs, I’ll download and check it out, I’ll post my review on it in a week. Thank you!
Awesome stuff !!!