There are many applications that RTM uses, which is why it took over a year to get it on the web! Here's a brief description of some, but for more and in depth help, check out RTM's services web page.
Google Gears can be used to access your tasks even when you are offline. Simply install the Google Gears plugin and you are on your way! For more information and details, visit RTM's Google Gears page.
Twitter can be used in close conjunction with your RTM account. However you must have a Twitter account. Twitter is a type of short messaging application that is actually used in conjuntion with many different devices. With RTM it can be used to send yourself and other Twitter/RTM users tasks, update your tasks, and send yourself specific lists of tasks. You can also set up reminders through Twitter. All of these things can be done through Twitter directly, your phone, IM, or other 3rd party applications. To get the list of possible tasks and more information, click here.
RTM also works with Google Calendar. Google Calendar adds an icon to each day so that users can easily manage their RTM account by adding new tasks and editing new ones, complete and postpone existing tasks, and use Google Maps.
You can also access Google Maps directly from your RTM account. By clicking on the Locations link, a Google Map comes up for easy access. This can help you locate where your tasks are and what's on the way to plan your most efficient route.