I don't think you can go far wrong with MS Access. There is so much free information available about it on the Internet, this forum for a start!
I particularly like this
free online book which is for MS Access 97, however much of the information in it is still valid for today's Access applications.
In particular, part three, covers advanced forms. I am studying this at the moment with a view to creating my own custom properties of forms. I am discovering that properties give me an extra, and in some cases a much better way of using MS Access, but the main reason I am studying properties is to help me with VB.Net which I am also learning.
My theory is that if I learn how to handle them within the MS Access environment which I understand, I will have a better transition into VB.Net.
I was doubtful about the wisdom of sticking with MS Access, Hence my interest in VB.Net, However when I saw Luke's lecture, I realized that MS Access is the main work horse of many businesses, and there will be vast amounts of work for MS Access programmers for years to come.
Studying MS Access will give you a sound grasp of data structure, you can also pick up SQL , ADO and DAO.
Another presenter at the same seminar Peter Vogel suggested that it was a good idea to learn a cutting edge technology, XML springs to mind. he did point out that sometimes you would learn a new technology which would crash and burn before it was established!
The main advantage to learning the new stuff was that you could command a very good salary, and as the technology is new, no one knew how long projects would take! A very nice position to be in I am sure. The other technology he mentioned that was worth learning was Crystal Reports. Good Crystal Report programmers are few and far between and I understand that MS Access reports are a good starting point for learning Crystal as they are very similar.