PresenterMedia - I can say this is one of the best online services that provides bloggers with one of the best images.
Not only you can get stock images here, you can also get powerpoint templates, animations GIF, video files (or movies)
And you can pick and choose the size of these images.
Very cool! Another 5-star for this service.
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I have been using PresenterMedia for a few years now - and I really love it. They keep on adding more media to their site.