well, in the photoshop area
-the latest version cs3 is out wich will be the priceist
-there are lighter photoshop versions wich you most likely will find efficent
-there are trial of photoshop located here of older versions for you to try
Adobe - Downloads
-and if you search adobe labs you may find there cs3 [the latest version] beta tester too but that will still have bugs and etc.
Corel I have never used, I doubt it is as good since its not the industry standard and I know the lower photoshop version like elements are fairly afforable at least for you to get your head in the door