I think flashcards cannot be too early at any time as long as the baby has fun looking at them. They are sooo earger to learn and learn new things every day, every minute, so why not support them in learning. We found some Iphone apps with flashcards for Yannis, e.g. there´s one that shows animals, you can hear the animal name and what sound it makes (
http://itunes.apple.com/us/app/id426148813?mt=8&ls=1). And there are several others. Yannis likes it because the animals make a sound and we look through it together and he hears how the animals are called. Of course "real" flashcards and picture books are also extremely useful.