Look at current postings. 

Career Information from HBS
The web page of the HBS Initiative on Social Enterprise has helpful information about every part of a social enterprise job search, from defining your interests to the job search itself. HBS Alumni Career Services has lots of general career resources.

One-on-one support in developing a nonprofit career search: The MBA-Nonprofit Connection
The MBA-Nonprofit Connection (MNC) is a national nonprofit organization that facilitates the placement of business school students and graduates in nonprofit jobs. The MNC provides a variety of services that help to bring MBA skills and energy to the nonprofit sector while bringing exciting new job opportunities to the business school community. Serving as an extension to HBS Career Services the MNC provides both job postings and advice. One-on-one support in developing a nonprofit career search is also available through personalized Career Advising. For more information on scheduling an appointment with an MNC Career Advisor, please contact the Social Enterprise Initiative for a referral. (Please note that many of the job opportunities posted on this site are received from the MNC.)

Career resources for alumni moving within or into the nonprofit sector: Bridgestar
Bridgestar, an initiative of The Bridgespan Group, is an organization dedicated to building stronger nonprofit organizations by facilitating the flow and effectiveness of passionate and highly skilled leaders into and within the nonprofit sector. Working in concert with HBS, Bridgestar aims to attract, connect, and engage talented leaders—both established and aspiring—looking to bridge from the for-profit to nonprofit world. Bridgestar offers job postings, nonprofit board matching, and executive search services. Membership is free to HBS alumni.