windows 7 taskbar pin custom shortcuts to jumplist
Nevermind that this is way late, but Jumplist Extender sounds like it does what you were looking for.
so JumplistLauncher does what I want, but it doesn't allow me to enter arguments for vncviewer. However I found msdn's Jump List Sample on which I assume JumplistLauncher is based. I modified the code and made an app that reads a simple settings file in which I specify tasks (== exe path, arguments, title and icon) for the jumplist. This is basically everything JumplistLauncher does, but without the gui, and it does work with arguments.