One of the greatest things about Open Source Software is that so much of it is actually cross-platform–meaning it works on at least two operating systems. Since many people today (myself included!) work on multiple systems, it’s great to only have to learn one piece of software, instead of 2 or 3! The following list contains 5 of the coolest Open Source and cross-platform tools for productivity, and you can use all of these apps on Windows, Mac, or Linux.

Pidgin

Pidgin (formerly Gaim) is one of those must have apps for me. It’s multi-protocol chat client that supports pretty much every network out there, including Yahoo!, MSN, Google Talk, AOL, and even IRC! “Wait,” you may be saying, “How is a chat client a productivity tool?” Good question, and I have to admit, instant messaging doesn’t usually top my list of essential productivity aides. However, studies have shown that IMing in the workplace can drastically reduce the amount of email backlog and streamline communication. Also, more and more web-based productivity tools like Remember the Milk can hook into IM as well, effectively giving you a quick, desktop interface to their site. I use Yammer (a specialized micro-blogging service for business and other groups) with Google Talk through Pidgin. Since Pidgin also supports so many protocols, it helps keep a lean and clean desktop by cutting down on the number of individual apps I need to have open for my instant messaging needs.

• http://www.pidgin.im/ – Linux and Windows
• http://www.adiumx.com/ – Pidgin for Mac

GTD-Free

If you’re new to GTD or just need some help keeping in line with the Getting Things Done methodology, then GTD-Free is an excellent app to begin working with. Basically, GTD-Free aims to be a complete, desktop-based system for Getting Things Done, from task and project management to handling your digital “tickler” file. The great thing about GTD-Free is its simple, tabbed interface that guides you through the GTD steps: Collect, Process, Organize/Review, and Execute. If you’re stuck with a lot of stuff in your head, and not sure how to get it out and get it done, then GTD-Free is for you! GTD-Free is also a “portable” app, so you can easily put it on a USB drive and run from anywhere!

• http://gtd-free.sourceforge.net/

Mozilla’s Ubiquity

This is an especially cool one, and it’s even cooler if you already have an affinity for the command line interface. Basically, Mozilla’s Ubiquity (not be confused with the Ubuntu installer provides a natural-language, command-line interface to the web. It provides advanced search functions for sites like Wikipedia and Flickr, along with tight integration with Google services like Maps and Gmail. Suppose I want to email John Smith…all I do is hit a keyboard shortcut and type “Email J” and a suggested list of contacts pops up. I select the correct one, and I’m presented with a Gmail Compose window. Then I’d like insert a link to a Wikipedia article…same drill. I hit the keyboard shortcut, and type “Wiki Elephants” and then click on the “Link-to-Wikipedia” option. Think of it as Gnome-Do, Quicksilver, or Launchy for the web. I’ve provided links to the official introductory blog post, as well a great guide from Lifehacker on using Ubiquity.

• http://labs.mozilla.com/2008/08/introducing-ubiquity/
• http://lifehacker.com/5145709/make-ubiquity-your-ultimate-firefox-commander

Mozilla Prism

Prism is another project from the Mozilla camp that has really been a productivity boon for me. It’s a single-site browser, meaning it’s basically just Firefox with no chrome (forward/back buttons, etc) and meant for tight integration with the desktop. Sounds a bit crazy at first, I know, but now I keep my Gmail, Google Calendar, TiddlyWiki, and Toodledo todo list all in their own little windows minimized to my system tray. Keeping them separate from my browser lets me have them instantly available without cluttering my regular browser. When I just want to plow through email, I can do that without the temptation of opening another tab to check my blog stats. Plus, Prism windows are much quicker to start up than a full Firefox session, so doing a fast calendar check is actually fast! An added bonus is that when Firefox crashes (and let’s face it…it will crash) it doesn’t take my essential productivity tools with it.

• http://labs.mozilla.com/projects/prism/

ThinkingRock

Our final killer cross-platform, Open Source tool is ThinkingRock, another GTD specific application. Much like GTD-Free, ThinkingRock helps keep you learn and implement the GTD steps, with an interface geared toward keeping you planted on the David Allen Path. While the interface is a bit more complicated than the one offered by GTD-Free, ThinkingRock is also a bit more powerful. It has all the support you need for fully managing your tasks and projects, as well as viewing various advanced reports on all your action items. One feature that I think sets ThinkingRock apart from many other GTD software projects is the ability to add criteria like Time, Energy, and Priority to you tasks, so if you’re feeling tired, you can easily find the tasks that the require the least effort to accomplish! Definitely worth a look.

• http://www.trgtd.com.au/index.php

I hope you may have found new bit of software that you can use to enhance your productive flow on all operating systems. Have you used any of these before? What other cool bits of Open Source and cross-platform software do you use? Let’s take it to the forums.