There are plenty of great, free Getting Things Done apps out there. If you’re a fan of David Allen’s productivity system but can’t do paper and don’t have the cash for a commercial program, this is the collection of applications for you.

The following is a list of nineteen free GTD apps for Windows, the Mac and Linux. Excuse me if I cheat by adding a web app here and there.

iGTD

Of the free GTD apps for the Mac, this is currently one of the most popular. Many people swear by it. You can get both the stable 1.4 release and the alpha preview of version 2 for free. If you’re a Quicksilver geek, iGTD has some slick integration built-in. Get it here.

What’s Next?

This is another Mac-based app. Some of its unique features include mini-wikis for each project (projects in the GTD sense, of course), and a focus mode that darkens portions of the screen so you can focus on getting organized. Get it here.

Chandler

Chandler is an app for Linux, Windows and Mac platforms. It’s got a bunch of great features including collaboration, advanced calendaring, and multiple contexts. The only thing I’ve seen people really annoyed by is its occasionally sluggish performance. Get it here.

Todoist

Todoist is a web application that’s compatible with GTD methodology. It’s a task manager with Gmail, Firefox and Quicksilver integration, calendar view, and deep hierarchies for projects and tasks. Get it here.

Jello Dashboard

Jello Dashboard is a free Getting Things Done plug-in for Microsoft Outlook. If you’ve always used Outlook to manage your data, your tasks and your day, this may be the ticket for you if you want to implement GTD methodology without leaving the comfort of your favorite app. Get it here.

Evolution

Evolution is the Linux counterpart to Outlook, the app that many switchers flock to in order to fill the void. Aside from having a bunch of features that Outlook doesn’t, you can set up a GTD methodology fairly easily with this app. There are a bunch of plugins that can add to your system. Get it here.

Actiontastic

Actiontastic is a nice Mac GTD app with a simple, uncomplicated interface. It has just the right level of functionality so you can get a good, effective GTD implementation going without feature bloat turning your system into a monster. Get it here.

Next Action

Next Action is a Google Gears based GTD app, so it runs on any operating system that Google supports with the Gears engine. Add this app to your list if you’re after something that you can use on pretty much any of the mainstream operating systems. Get it here.

GTD TiddlyWiki

Remember the recent Lifehack article about personal wikis that mentioned TiddlyWiki? GTD TiddlyWiki is an adaptation of that software so it can be used for GTD productivity purposes. Another one for the cross-platform crowd. Get it here.

FusionDesk Starter

Windows is fairly light on good GTD apps, so you might be surprised to see another free offering in this list. Although it’s a lesser version of the paid app, FusionDesk Starter still allows you to organize your tasks into folders or with filtering (the absolute minimum requirement to implement GTD), and is built on GTD methodology. Get it here.

Nozbe

Nozbe is an interesting online GTD app with a focus on collaboration with small teams, and accessibility from most mobile devices (of course, all the pictures are of an iPhone). Individual and business accounts are both free. Sign up here.

Check Off

If you’re looking for a really simple GTD implementation, get Check Off for Mac OS X (10.5.2+). It’s a to-do list that drops down from the system-wide menu bar, and since it’s hierarchical, it can be made into a bare-bones GTD task manager. Get it here.

Beeswax

For Linux. There’s a bunch of people online who are still talking about Lotus Agenda and how it was the best productivity app they ever had, and that nothing since has quite beaten it. The last release of Agenda was in 1992, and even 16 years later people want something just like it: enter Beeswax, which is designed for just that purpose. If you like command-line productivity, get it here.

Thinking Rock

Thinking Rock is a Java app, meaning it’ll run on Windows, Mac OS X, or Linux. If you don’t want an app that has a lot of extra features, something that just lets you run a basic GTD system, you might want to try this one, particularly if you need wider cross-platform support (IE, anything that runs Java). Get it here.

Toodledo

Toodledo is a web-based app with mobile accessibility and collaboration features. You can organize and annotate your tasks in just about any way you like—folders, sub-tasks, notes, contexts, goals, time estimates, just to name a few of those mentioned on the site. Get it here.

Remember the Milk

Remember the Milk is perhaps one of the most popular web-based task managers out there and it’s one of the easiest to implement a GTD methodology with—in fact, there’s a post on how to do this on their official blog. There are a million ways to interact with your RTM account, including Twitter, iPhone, Google Calendar and the list goes on. And on. Sign up here.

Things

Perhaps this isn’t the list for Things, since it won’t be free in the future, but it is right now—so it counts. Possibly the most attractive GTD task manager for OS X in existence, the way Things organizes data is both elegant and practical. There are a couple of annoying interface issues, such as no sidebar dragging, but they’re pretty minor at the end of the day. Get it here, before it no longer qualifies for this list.

MyLife Organized

MyLife Organized is a Windows GTD app with a free version. If you’re using Firefox you might get a malicious site warning trying to enter, but there’s nothing wrong with the site—Google just doesn’t bother to check what they’re blacklisting before tarnishing the reputation of a good developer (another good reason not to put all your eggs in one basket as many people are doing with them). Rant aside, there aren’t many Windows GTD apps around, so see if the free version of MyLife Organized tickles your fancy. Get it here.

Action Tracker

Action Tracker was built with FileMaker Pro, which means you can approach your GTD software as a database rather than a task list, if you prefer to think that way. There’s a FileMaker file download as well as a stand-alone executable, so you don’t need to buy anything to try this out. Get it here.