I hope that the "help" Shepard can bring is the Rachni. Those fuckers would be awesome.
The list is pretty large and varied if you think about it, and can be hugely affected by your decisions in ME1 and ME2:
Possible spoilers ahead of course.
The main council races, obviously
The Rachni (did you kill or save the Rachni Queen)
The Quarians (did you side with Tali or Legion during their argument...plus, how did you resolve the political issue that was affecting the migrant fleet that was intertwined so heavily with Tali's trial)
The original Geth (again, who did you side with in the argument)
The Geth that supported Saren (did you destroy them, or alter their programming on Legion's loyalty mission)
Cerberus (did you destroy the Collector base, or keep it for the Illusive Man)
The Shadow Broker (highly dependent on the DLC you may have completed)
If Bioware don't fuck this up they may end up with an RPG that actually has more variations on shit than even Deus Ex.