I got a call from this number and they left a brief message (which was cut off) for the non-profit I work for. Are these people legit? I am wondering how they associated my home phone number with the company I work for and why they would even call. My home number is not listed with the non-profit.

Since there is so much personal information out there on the internet, they may have found something that lists your employer, such as a Facebook page, Linkdlin profile, or another web site that lists phone numbers and personal information (there are quite a few out there, some even showing a picture of your residence in case you were not aware of that).

No doubt they have some con in mind such as this one or a variation of it:
http://www.ic3.gov/media/2014/140627.aspx