What is it?
Set up a free blog on a website such as wordpress to keep track of both your reading and volunteering, and encourage others to do the same!
Where will it happen?
You can write it wherever you want, on the sofa, in bed, at the library, whatever suits you best.
There's loads of free blogging platforms, from wordpress.com to tumblr.com. Start by doing some research to find what blogs are already running, then brainstorm what will make your blog unique.