|MadSci Network: Computer Science|
First, a more general point: you will probably change subjects between now and the time you get a PhD. My undergraduate major was in English, my MS was in computer science, and now I'm working on a PhD in computer science and cognitive science. This is a good thing; being able to draw on lessons from several different disciplines gives you a different point of view from your colleagues. Now, computer science jobs. With a PhD, you're probably destined to do research, teach, or both. This would most likely involve a position at a university, but there are also private, corporate research facilities. Programmers and software engineers tend to stop at the Master's level. It's hard to predict how the market will be ten years from now, but right now industry can't seem to find enough programmers. Web companies, small businesses, very large businesses like Microsoft, computer game companies ... unless things change drastically, you should have no trouble finding a well-paying job in an area that interests you. Good luck!
Try the links in the MadSci Library for more information on Computer Science.