If you use the OmniFocus task manager on Mac, you have a number of syncing options, but you might need to sync between computers running other OSs. Vincent Danen tells you how to use the Web-based Spootnik service to handle it.
OmniFocus is my GTD app of choice on the Mac. Unfortunately, you need a Mac to use it (or an iOS-enabled device for the iOS version of OmniFocus). If you're all-Mac, this doesn't pose a problem. If you're not all-Mac (using Windows or Linux at work, or at home) then the usability of OmniFocus is stunted somewhat. It's easily worked around if you carry an iPhone or iPod Touch with you all the time, but a bit of a pain nonetheless.
The nice thing about OmniFocus is the many ways it can sync. You can use MobileMe to sync, Bonjour syncing for local networks (i.e., a desktop and laptop on the same network could use the same OmniFocus data), via disk or WebDAV -- although WebDAV has certain stringent requirements that can make it tricky to set up.
Enter Spootnik. This Web-based service allows you to synchronize OmniFocus easily and comes with a number of plans. The free plan allows for WebDAV synchronization, which is great if you use OmniFocus at home and at work. And it's also easier than trying to monkey with a DAV server yourself. The solo plan, at $3/mo, provides a Web-based frontend to OmniFocus.
You still get the WebDAV-based sync, but you can also use OmniFocus when you're in front of a Linux or Windows computer by utilizing the Spootnik web site. Other plans also include the ability to synchronize with Basecamp projects, which can be indispensable for people that also utilize Basecamp.
Sign-up is free, and Spootnik offers a 30-day trial without taking any credit card information. So you really do get to try it out fully before you pay a dime, or even give out your precious credit card information. This feature I like.
Once you have received your confirmation mail and signed up, the Spootnik site gives you clear instructions on how to set up the sync in OmniFocus. Once that is done, the Spootnik page should quickly indicate that OmniFocus has been successfully linked to the account. If you use OmniFocus on iOS or on other Macs, you can repeat the same steps to synchronize with the same WebDAV server that Spootnik provides.
From there, you can now visit https://www.spootnik.net/ofocusweb/[user] and get a web frontend to your OmniFocus data.
The web interface is quite simplistic, but is definitely adequate. It doesn't have the same features that OmniFocus itself has, however. You can search for tasks by name. You can list items in particular contexts; for instance, if you define contexts like Home, Work, Away, Computer, etc., you can use the "@" link in the web UI to get a pull-down of available contexts and select one accordingly. The little clock icon shows the equivalent of a tickler: it lists all upcoming tasks that have not been completed, along with their due dates.
Clicking on an item in the list highlights it and allows you to edit the task name, delete it, or add a sub-task. Clicking the checkbox beside a task marks it done.
The UI allows you to add new tasks and projects very easily, so if you are working away and need to quickly add an item to the list, you can do so very painlessly.
There are some drawbacks, however, and hopefully these will be addressed with a future version of Spootnik. There is no way to flag an item, which is a useful feature in OmniFocus. There is also no way to see notes that you can associate with an item either, which can be quite a serious drawback, when you need that extra information.
The Project Filter in OmniFocus is also a really great way of visualizing your tasks, because you can use it to view open projects, active projects, projects that have been completed, or those on hold. Spootnik offers nothing like this.
Having pointed out the drawbacks, Spootnik's biggest feature is bridging the gap between Basecamp projects and OmniFocus, effectively allowing OmniFocus to be a frontend to Basecamp in many respects. So while it may be rudimentary for its own web interface (and hopefully these missing features will come in the near future), it is certainly more than usable in terms of looking up active items and logging new items as they come to you, regardless of what computer or operating system you are using. Likewise, if you only need to reference the information without all of the bells and whistles while on the road, you can forgo paying for OmniFocus on your iOS device and use Spootnik via Safari on it instead.
As well, the fact that you can use Spootnik for free to synchronize, using WebDAV, is a definite bonus. This takes care of the difficulties of properly securing and setting up a WebDAV-enabled service to properly handle it.
The downside is that you are trusting Spootnik with your data. Of course, if it's as simple as "buy milk on the way home" then it probably doesn't much matter who sees it. If it has to do with confidential business products or things requiring high security, using Spootnik is probably not for you. It does not store the OmniFocus data encrypted because it obviously needs to parse it and write to it. Access to the Web UI and the WebDAV location are all via HTTPS, so the data is protected in-transit, but if the Spootnik server were to be compromised in some way, your data could be readily available without any server-side protection. Weigh the risks and confidentiality of your data before deciding to use it.
Spootnik is neat, and seems quite reliable so far. I'm not sure if I necessarily need to pay the $3/mo for the web UI since I do have OmniFocus on my iPhone, but the ability to have it synchronized without being on the local network is nice, as is the ability to not have to go through the pain of setting up a WebDAV server on my own to access it.
Considering there is absolutely no cost to giving it a try, if you are currently using OmniFocus, you may want to give it a look.