well, i am not going now to make a research, but the first that cross my mind:
1.Qatar Foundations (we all know who is a Chairperson of it and Who has founded it and who is doing absolutely great job in it!)
2.Barwa (most of projects managing directors are qataries, not to mention the Barwa's chairmen office)
.. i am sure there are a lot lot more.. give me some time, i will meet more of them and give you more idea about it.. i am relatively new in doha anyway...