Windows 7 Taskbak aka super has many new feature for e.g Aero peek, Aero Snap, jump list and grouping of icons. Windows 7 taskbar lets you to group similar windows instances to save your taskbar real estate unfortunately grouping of icons of different applications is not possible.
But you can get such feature in Windows 7 with Win7Stack. WinStack is an easy to use application that enables you to add stack-like functionality to icons for the new Windows 7 taskbar. Basically you select the folder the use and the icon and Win7Stack will create the stack on your desktop. You can then easily pin the stack to your taskbar.
Win7Stack in Action
You can specify Your own icon for group applications with displaying styling as Grid or Fan Look with Aero interface.