My own work on this blog (writing, and any diagrams or graphs I make) can be used under CC Attribution. To attribute, please use a link here, or my name (Thomas Kluyver). If you are using my work, I’d be interested to hear from you.
Where I’ve used other peoples’ work, credit should be clear, e.g. in photo captions.
In blogging about peer-reviewed papers, I occasionally use images, such as graphs, from those papers. I believe that, as noncommercial review/discussion of the material, this falls under the definitions of ‘fair dealing’ (UK, where I am) or ‘fair use’ (US, where I assume the blog is hosted). If you own the copyright and feel wronged, please get in touch via the comments.