If you're focussed on public service, then the obvious choice is a masters in public policy or a masters in public administration. Johns Hopkins has one of the top schools for international public service, and that's worth looking at seriously. I'm not sure what the added benefit of an MBA would be.

I would also suggest you look at the dual degree GPPN programmes: http://www.gppn.net/?page_id=23

I think an MBA/MA dual degree program would be valuable if you want to go into a political consulting role, or another business where you want to keep a foot in policy or in politics.

As Duncan suggested, an MPP or a master in public administration (MPA) could be an option for you. These are policy-specific degrees, so they don't really leverage any business insights. Not sure what kind of role you're in, but if you're doing budgeting, analysis, etc., then a strict policy-oriented degree might be too limiting.

There are also MBA programs that offer electives or concentrations in government and public policy, which may be relevant for you as well. Since you call Johns Hopkins local, you must be in Baltimore, right? If so, George Washington isn't too far away - its full-time MBA program offers a specialization in public policy; and if you pursue the part-time program you can take electives in this area as well.

Thanks for all the advice!

I don't really plan on going into "politics" or political consulting, per se - I'm just in a position that's related to finance which is requiring more and more business-type skills. So I think I'll just look into a regular MBA, or maybe even one with a concentration in government (that George Washington program looks good, thanks for suggesting that, Ralph!)