Everyone is definitely giving great feedback here. My thoughts RE: specializing in non-profit work would be proceed with caution. I have a very strong background in volunteerism, did 2 internships with NPOs during undergrad, and have about 2.5 yrs of FT work exp at NPOs since graduating. What I've learned, especially in my yrs of post-undergrad work, is that non-profit work comes with its own special batch of challenges (like most types of work, I'm sure) that are particularly challenging to a young professional looking to establish themselves. While I am positive I want to continue on in public service, I'm not sure if it will be with NPOs. Part of this is due to a desire to actually make enough money to begin saving and feel financially secure. Currently, any major unforseen event (car accident/repair, serious illness, etc) is a HUGE stressor. I also can't travel as much as I would like to, and have a pretty limited 'fun' budget. Part of it is also because I don't feel there is a lot of room for advancement from entry level work. Thats probably less true for larger organizations, however I've also seen that the mid-level work that does exist doesn't necessarily correlate to substantial pay increases. I see myself leaving NPO work for quite awhile, and maybe returning to it in my mid-late 40s.
So I guess what I'm trying to say is that a focus in NPOs may limit your possibiltiies, but - for instance - an MPA with a focus in intl devt can be useful at an NPO, in the government, with consulting companies, etc. Personally, I want to ensure I don't pigeonhole myself.
Best of luck!