In Mass Effect 1, you get several options regarding the composition of the Citadel Council - you can either save them from a certain doom, or allow them to perish and form a new council (either one of all humans, or one with the existing races still included). You also get to name an Alliance member to the council.
These didn't have much consequence in Mass Effect 2, but it seems like it may end up being more relevant this go around. What changes can be seen a result of these choices in Mass Effect 3?