I think this has already been said, but I'd like to put it thus. First you need to decide why you're "getting back in the game". Is it to change careers? Just have some fun? Expand your horizons? Write programs to help you with your mathematics?
If you intend to do this as a means to make money (as a primary profession), you will need to investigate what kind of jobs interest you most and learn the technologies that are associated with those. For example, if you want to write web applications, you'll need to learn the basics of GUI (this is as much philosophy as it is technical) and the tools to render and implement said elements. Obviously that will involve HTML, CSS, Javascript, and possibly Flash. Flash has the added bonus of allowing you to develop iPhone applications, if you get the latest.
That's just one example. If you're doing it for any of the other three reasons, then the first thing to do is to figure out what you want to ultimately wind up with... a game? a useful app for your phone? a gag app to send to your friends? It can be anything. Once you have that figured out you can alter this question and quickly people will tell you what the best way to implement the idea would be.
If you used to write c/c++ then none of this will be difficult, but there is SO much to learn that simply asking "what" should I be doing is sort of like saying "I used to know how to walk but I've been in bed for the last 10 years... now that I'm up again, where should I go?!"