Micro-volunteering

Recent term coined to describe volunteering done in small chunks of time, even in minutes. While micro-volunteering can be done in various ways, it most often is a sub-set of virtual volunteering and is done online or via smartphone.

Aimed at charities and nonprofits interested in exploring the world of microvolunteering. , 2011, pp. 42
"Donate Your Brain!" Microvolunteering Project of Tech Soup
Great example of how to create and run a micro-volunteering project.
We Are What We Do

A UK-based site that "creates stuff that makes it easier for people to do small, good things everyday," which they call "actions."