I love it when Scott Hanselman updates his Ultimate Developer and Power Users Tool List for Windows. I saw Bins and immediately went and purchased it ($4.99 PayPal). For each program pinned to the taskbar, you can create a group and put four shortcuts in the space of just one regular pinned icon. You can even choose which is the default click program, or hover to see all the programs in the group.
[The same author created the very useful (and free) Fences)]