Whilst application shortcuts and programs can be pinned to the taskbar in all recent version of Windows including Windows 8. I can't find a way to pin folders to the taskbar for quick access in Windows 8.
What ways exist to achieve this ?
This is what you need to do in order to pin a folder to the Taskbar, and it will work in both Windows 7 and Windows 8:
Source: 7Tutorials (includes screenshots)
In windows 8.1, if you already have explorer/a folder pinned to your taskbar (I believe one is pinned by default), you can just drag and drop a folder onto the already pinned icon to add it to the list of sub-pinned folders.