Side projects

I recently had a conversation with a friend about work and the discussion got to the point where one of us had the question:

Why are we doing what we are doing?
A handful of answers popped up, some were rather ordinary ("for the love of programming", "for the money") but none of them were as frightening as this one:
For the appreciation and acknowledgement.
It is obvious that almost everyone seeks for these two things and I'm not different from others in this aspect. Going through the deck of Zach Holman's presentation made me realize that both appreciation and acknowledgement can be earned by doing things that are not a must.

Now for me as a programmer there is a self-evident choice of doing side projects. Being a co-founder of a company and running side projects is rather controversial but in order to keep going even in the worst times there has to be something to rely on. I'll give it a try and keep posting the results here.

What are your side projects?