An update that comes along with Mango is the Windows Phone ‘Web Marketplace’ which lets you search, find and browse Apps via your browser, and then have them automatically sent to your phone, and installed without any interaction on the actual handset. Not got Mango yet? Check out how to Force the Mango Update now!
The Web Marketplace also remembers which Apps you have already paid for or installed on other devices, and will let you easily “Reinstall” those Apps to your phone. Check out the video below by @BenThePCGuy which has a walk-though of downloading an App from the Marketplace to the phone.