You could look into what other people are doing, for example at
The Code Project or
Planet Source Code, here you can get ideas you want to try yourself.
Write your own version of current applications you use? Or any programs/features you're missing that you could do? Automation of common tasks that could save you boring work and time?
General topics of programming, is there a field you don't know good enough? Browse the
forum index and see if there is one of interest.
How about the threads posted at forums, for example
Today's Posts, can/could you answer these questions? If not you have something to learn, if you have interest in the topic. Even a short question about some detail may give you the inspiration to write a whole application.
As you may see
what you can do is determined by knowledge, what you know and what you can learn, and in some respect time & money -
what you want to do (if anything
) is determined by your own imagination and inspiration from others.