Errr... your Mac OS should come with iPhoto, no? Think that's the best program to use, it also has an a-mayyyyyyy-zing 'enhance' button 
Otherwise, Preview has the basic photo adjustment functions but you'll have to organise your photos by the Dewey Decimal system! Eek! Sorry, wrong forum!
Organise the photos on your own.

Otherwise, Preview has the basic photo adjustment functions but you'll have to organise your photos by the Dewey Decimal system! Eek! Sorry, wrong forum!
