I always saw it as the Rebels being the Allies and the Empire being the Nazis from WWII. Its just that the star wars Nazis spoke brit english instead of German.

Thats what Lucas was thinking when he wrote the films.  The Empire bears alot of resemblence to the Nazis - they are both racist, they both think one race is superior (aerians and humans), they both enslave a race they think is inferior (Jews and Wookiees) and force them to work in camps, the leaders of both rose to power 'legally' in democracies, and proceeded to completely take over the governments and rule as dictators, both of their elite shocktroops are called... STORMTROOPERS!  Hell the TIE pilots even fly like German pilots.  I wonder if the real stormtroopers had the accuracy problem.

The Liberation of coruscant picture was deliberately derived from the Iwo Jima Picture =P (Master of the obvious Pin awarded!)