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There are several online places where you can find free Stock Images for your website or blog that are royalty free. Stock.xchng is one of the most popular ones that I use myself as they have a cool "Randomizer" feature which will randomly show you a stock photo which can help inspire you in some cases to write a blog post around the image.
Stock.Xchng is one of many free online image galleries and one of the ones I highly recommend though you do have to check the usage rights of each image as some have stipulations. It is a good idea to put a credit in the alt tag or a caption for the image to the originator as well.
What I am looking for is not a free photo stock site, but one that has hand drawn or digital art instead.