With over 10 million images, Shutterstock has the biggest inventory of images for designers with a subscription-based program and new "On Demand" subscription plans. Great value for money if you download many images per month.

For photographers, it's one of the most lucrative of all the sites and the community is awesome

Fotolia brings good income to photographers and is in my top 3 for making money. Their upload features are very user-friendly.