I hate to do this in a ZB forum, but the most used application in that list is by far Photoshop. Photoshop is probably the most widely used application in all fields. The training for Photoshop is second to none. Total Training for Photoshop CS, or Photoshop 7 (8 DVD set) will turn anyone into a photoshop expert in a matter of weeks.
Photoshop user Magazine is also full of great tips, but you wont need more than the Total Training DVD set. Scott Kelby (From Photoshop user Magazine) also makes Photoshop Training DVD’s that are not total coverage of the application, but he takes you through techniques for particular areas that are useful throughout any project, that are equally as good as total training DVD’s, but are not the same thing.
If you really have to ask that question I would say you should start with a package like photoshop. Most other interfaces for other applications take many things from photoshop. You always here people say something in tutorials like “If you know photoshop, this part will be easy”.
Another thing about Photoshop is you’ll still use it with every one of those applications on that list when your ready for more. Sometimes you don’t actually need it with ZB, but it’s just such a great application you want to.
It all has to start somewhere, and if you want to lay a great foundation in your digital skills, or have skills in an application that is used throughout many industries world wide Photoshop is the best place to start.
That’s my opinion, and an honest answer.