I work for a nonprofit and i love it!
The only thing you need t be aware of is this industry's ridiculously high turnover rate. A lot of times people come to the field starry eyed and idealistic, and leave (1) disappointed in the pay or (2) discouraged about of office politics / advancement opportunities.
check out
www.philanthropycareers.com, www.idealist.org, www.asi.careerhq.org, or your local newspaper for job listings in this sector.
i'd also advise you to check out a salary / compensation survey for your field / desired position in nonprofits of similar size OR in your metro area to get a better idea of the pay you'll be competing for.
Not saying any of this to scare you away, but to give you some things to ponder. I enjoy working for my nonprofit... it's a great feeling using your skills and talents to benefit a greater good!