To get started with ThinkingRock you'll need to grab the appropriate package and have Sun Java installed. The Linux build includes a shell script to fire up ThinkingRock; see the install instructions. ThinkingRock is not released under a free software license, but it is freely distributable, and the creators have indicated that it may be relicensed when the 2.0 version is released.
ThinkingRock is not your everyday task manager. If you're not into the Getting Things Done method of task management, ThinkingRock will feel more than a little awkward.
When you first start ThinkingRock, you'll need to create a data file to hold your tasks, then define your contexts and topics. Contexts are collections of tasks that go together -- for instance, installing updates and doing system administration on servers, or processing invoices and paying bills. Topics can be used to group tasks by the area in your life that they fall under -- for instance, you might have topics like "financial," "work," "personal," and so on.
After you create the topics and contexts, you start collecting thoughts -- basically doing a brain dump of everything that you need to do or process. You then process that stuff into ThinkingRock in three categories -- actionable items, information, and future items -- or just delete it altogether if it's not actionable or useful for future reference. That means you can do a brain dump using ThinkingRock and not worry "is this actually something I need to do" while you're doing the brain dump. Future items and information can be re-reviewed at a later date and processed into actionable items if their status changes.
From there, you're guided into reviewing the actionable items and creating lists of things to do. ThinkingRock helps you organize actionable items into usable form as scheduled items, projects, delegated items, and things to do ASAP. Then you can review actionable items, and start walking through your tasks.
You can review scheduled items, or view tasks that are "ASAP" when you don't have a deadline pressing on you, or review delegated items to see if the people you've delegated work to have completed their tasks.
One thing you don't need to find time for in your busy schedule is saving your data -- ThinkingRock does that automatically, so you don't have to worry about it.
What if you're going to be away from your computer? No worries. ThinkingRock allows you to generate a report of your next actions as a PDF file, so you can print out your list of things to get done. One note -- ThinkingRock doesn't actually tell you that it's generating a PDF or where it's putting it, which is a bit annoying. The first time I ran a report, I was wondering if the function wasn't really ready yet, until I checked my home directory and found a PDF prefaced with "next-actions" and a long date string.
ThinkingRock is a nice application, but I do have a few minor quibbles with it. While I appreciate the desire to enforce the GTD process, I'm not too crazy about the fact that you can't simply create an action -- you have to walk through the steps of collecting a thought, then processing it. This is probably a good thing for day-to-day work, but when you're doing the initial setup to integrate ThinkingRock into your daily schedule, it's a pain.
I like to tab through applications rather than having to mouse my way around an interface, but ThinkingRock's tab behavior is less than desirable. For example, when setting up contexts and topics, you'd think that you could tab from the name field to the description field when creating new topics or contexts, but no -- as soon as you enter the name for a topic or context, tabbing will bounce you out of the name field and back to the toolbar. You can arrow back and forth, but it's a bit counterintuitive.
I've also noticed a problem with ThinkingRock when running under Ubuntu Feisty with Compiz turned on -- namely, that help windows and other dialogs appear grayed out, so you can't read the contents. I'm not blaming this on the ThinkingRock developers, but it's worth noting that if you're using a distribution with desktop effects enabled, you might run into a few glitches with ThinkingRock.
Those considerations aside, I've found ThinkingRock to be very useful and worth taking for a spin. It's a great application for enforcing the GTD methodology -- assuming you can stick with firing it up every morning (or just leaving it running) and making it a part of your routine. I haven't found any other applications for Linux that support the GTD methodology so closely.