Do you use images in your blog posts? I do, sometimes, when I'm not too lazy to hunt down the perfect image or grab a relevant screenshot. Lately I've been using Shutterstock because they were kind enough to give me a trial account so I would try them out.
I also use Flickr (this post shows you how to find photos on Flickr). Yesterday as I was going down rabbit trails, I discovered a tool - plug-in - for Wordpress called Photo Dropper. This tool makes it super simple to find and add photos from Flickr to your blog posts. Check out my 4:46 min video see how simple it is. (Click here if you can't see the video in your reader.)
If you're using a blog platform other than Wordpress, then you'll have to add photos manually, as far as I know.
What's your favorite source for images to illustrate your blog posts?