The Minimize Group context menu from the taskbar in Windows XP and Windows Vista has been removed from Windows 7. The new "alternative" is to wiggle a window (or use a Windows key shortcut) to hide other windows. This is not the same as Minimize Group, which hides all the windows in a specific group. This is a feature I used every single day on Windows Vista and is now gone from Windows 7. Please add this feature again to the taskbar context menu.
Add a "Minimize Group" option to the context menu, similar to the "Close all windows" option which still exists.
Alternative solution reported by xombie:
If you Shift+Right click on the application's taskbar button, you'll get the old context menu, and Minimize All Windows is present.
The old menu is still available using Shift + Right Click, though it would be much better if that option additionally was available in the new menu.