Here's my experience:
I wrote an embeddable open source HTTP server library back in '05-ish, a couple years after high school. It was a 3-4 month project maybe, and I got invitational emails from a bank company in France, a software firm in Arizona, and another in Toronto.
A year later, I wrote this article on screensavers and got an offer from a local company.
Later that year I wrote an angry petition to Microsoft and landed an interview there.
I never took any of these jobs, sometimes because I wanted a degree first and sometimes because they wanted me to have a degree first (make of that what you will) -- but I think it's evidence enough that working on your own projects out of your own interest is a huge boon to your employment prospects.
The only thing to be careful of is getting behind the times. I mean, if I wrote that screensaver article now, people would think I'm nuts.