Terms of use are critical. Most allow for the revocation of access if the API provider decides to do so. If that happens to you, you may have little recourse. Make sure you understand the terms before you build a business on top of someone else’s API.
Flickr
Five sources of free photographs for your blog
How to write attributions for the Creative Commons licensed images you use on your blog
I’ve found that pictures shared under a Creative Commons (CC) license (of all flavors) are a great resource for bloggers who want artwork to accompany their posts. I’ve also realized that not everyone, myself included, has always done an adequate job of meeting the attribution requirements of CC licenses. To help remedy this, here are my recommendations for doing this properly in a blog.