Revised: yet another great service ruined by corporate greed... dramatically higher prices, confusing credits.
Huge selection of photo and vector art, good search/lightbox capability,
low cost, essentially unlimited use (for many purposes), easy pay ‘n download.
My favorite feature? Ability to download reasonably clean watermarked comps so we can play around with storyboards and mock-ups until we decide exactly which ones to use.
What’s not to like? http://istockphoto.com