Mine is driven by an eccentric fear of how the economy is changing and assumptions of what it will look like in 10 - 20 years, coupled with a pessimistic view of human nature (but not people, just the way non reflective people behave). I'm trying to financially secure my son's future.
http://startupclass.samaltman.com/courses/lec10/
I personally use this as a way to brainstorm new ideas on marketing for my projects.
This is a piece I wrote on Quora, covers 20 startup topics with links to articles. It's a basic summary of what I leant from the business side of startups: http://www.quora.com/What-should-you-do-if-you-want-to-be-an...
I'm focussed on trying to make a successful startup. I think it really helped when my daughter (7 months old) was born, kind of pushed me to work away from my shitty day job.
My site will be ready in 1-2 months, if you're any good at UI/UX PM me and keep in touch, and maybe we could do a trade, you could have a look at my design, and I can teach you the marketing side - and, more importantly why I did things this way.
We'll make it though.
That drives me to work harder, keep improving my skills and stay on the lookout for projects that will make me valuable on the developer market and maybe bring in revenue.