I certainly think you should start right away working in the field you seem to care about and want to dedicate your professional life to. I think it's important to start early, mostly so you gain a better understanding of what's available. I think that many people assume there are only a handful of jobs—working in non-profits, being a professor, working in politics—when, in fact, within each of these professions, there are dozens upon dozens of more specialized jobs. I think that exposure is so important in order to build your expertise. Some of my earliest jobs made such an imprint on me—they have stayed with me in more ways than I would have imagined.
Specifically I would obviously look to the local organizations that seem to reflect your politics, such as the local YWCA or maybe your campus Women's Centers. I would even suggest that you start TA’ing in some of the classes—or even working with a local high school or after school group to share your knowledge and interests.
There are job listings on feminist.org, Third Wave, idealist, etc. and other places that seem slanted toward your priorities.