With Windows 7 beta 1, when you drag a file onto the Taskbar, you are given the option to pin the file to its associated application. So if you drag a Word document onto the Taskbar, you get the option to “Pin to Word”. If the application is already pinned to your Taskbar, the file is pinned to it and will appear in the app’s right-click menu.
On the topic of the Taskbar, applications that are pinned to the Taskbar automatically have shortcut key combinations assigned to them. To launch the first application located on the left of your Taskbar, simply press Win+1 (where “Win” is the Windows key). Win+2 will activate the second app, Win+3 the third, and so on. (These shortcuts also work in Windows Vista for icons on the Quick Launch toolbar, but it’s worth mentioning here since this is a very convenient trick but not widely known.)