Source: http://feeds.gawker.com/~r/lifehacker/full/~3/9V1ztfnU4o0/use-gmail-tasks-as-a-desktop-app
Reader Evan writes in with his simple guide to putting Gmail Tasks into a desktop application, using the built-in application shortcuts feature in the Google Chrome browser—simply navigate to https://mail.google.com/tasks/ig in Chrome, use the Create Application Shortcuts feature on the menu, and resize the window down to a smaller size. You can then access your tasks through a desktop shortcut anytime you want.
The process isn't anything new to most Lifehacker readers, but it's a great idea that gives you quick access to your Google Tasks, which can then be accessed anywhere from your mobile device or iGoogle page. Hit the link for the walk-through, or you can add Gmail Tasks to your Firefox sidebar instead. Thanks, Evan!
Update: Looks like there is a known bug with the iGoogle ! gadget not working properly in Chrome which is causing a blank page after the first time you view it. Hopefully Google will fix this soon, but until then you can use the Adobe AIR version of Google Tasks suggested by Steve below, or use Jazzva's suggestion to use the Prism extension for Firefox's Tools -> "Convert Website to Application" option to get nearly the same window as the screenshot. Sorry about the trouble!