I like using images in my blog, it spices up posts and makes the blog look more attractive. It was not easy to find images that I knew for certain I was allowed to use. But then I came across Skellies post A Complete Guide to Finding and Using Incredible Flickr Images and since I enjoy Flickr it suited me perfectly.
I decided to use images under the Attribution License since it allows me to modify the images (I often prefer to crop them). And my blogs are in a grey zone between commercial and non-commercial spaces, this license is valid in both. I do have to credit the author with a link back to their profile but that is a very fair deal. Flickr has an Attribution License search page.
Skellie followed up with The Flickr Guide, Part 2: How to Caption or Credit Photos in Posts. I decided to use a note at the end of the post, it is easy and makes sense to me.