There have been other online third party solutions such as TimeBridge, but they normally require you to join their service and you have to install some desktop software and require a fee in order to work. Tungle.Me avoids all of those things, although it is recommended that you install the Microsoft Outlook connector add-on for best results.
Here’s a short screencast of how Tungle.me works. It also includes a cool widget that you can embed on your blog or website.
Note: I’m hoping this service will work with our upcoming accounts, especially for large conventions and events that involve many schedules.