Nothing makes me feel more productive than creating an experiment / process that can run in the background while I do other stuff. TBH, I usually end up spending so long tuining the background process to work perfectly that I lose any time that I might of gained. Or otherwise I just watch the background process and lose the point of the whole thing.
That aside, I've been leaving my fractal code running in the background while writing emails etc. and this has led to some nice images. Rather than creating a new post for each of these, I've started a static Fractal Gallery page, where I'm going to be adding new images as necessary (either when finding cool stuff, or developing the code / maths further).