As with everything, it depends on your subject area. Generally speaking if you are studying science or engineering (as I suspect you are) then there are plenty of opportunities to work in industry. This can be either immediately after a PhD or after further years of postdoctoral experience. The biggest entry point into industry is as a researcher, with the prospect of moving through to a more managerial role. Many blue chip firms recruit PhD graduates directly into their management training schemes. Further study after your PhD could take you into the very lucrative areas of patent law or management consultancy. Those who are less money motivated could go into teaching, publishing or technical writing/journalism. Others use their lab experience to move into selling/marketing laboratory equipment or providing technical support for the same. There's a lot of other options I'm sure I've left out, but no doubt other visitors to the forum can add to this list.