Delta = MD
Atlantic Southeast = CRJ-200, CRJ-700
Comair = CRJ-200
Atlantic Coast (Delta livery) = 328JET, (United livery) = CRJ-200
Continental = ERJ-145
US Airways Express (Piedmont, Mesa, PSA) = ERJ-145, Dash 8 (-100, -300), 328 Prop, CRJ-200
GSP gets pretty much everything CAE gets plus American Eagle ERJ-145's, US Airways Express B-1900D's, and Delta 737-800's.
As for spotting, in CAE you can pretty much see everything from the terminal. There are rocking chairs in the middle to sit and look out the tinted glass at the apron and main runway. GSP has a park in the middle of its terminal that spotters used to go to but I have never been there and don't know if it is still open.