To further jump on the bandwagon, my last 7 job offers came about in part due to my CPAN code. My current job pursued me purely because of my CPAN code. OSS is the best advertisement a programmer can have because:

• You now have code samples which many interviewers are looking for. Until I started doing CPAN stuff, I didn't have any code samples because everything I'd done was owned by my employer at the time.
• If your name is attached to important projects, you gain importance. Let's say your son managed to get a device driver into Linux. Or, maybe he rewrote a subsystem for Firefox so that it worked on OSX better or fixed some major porting issues for OpenOffice on Win64. These are huge feathers in the cap and prove that he has "real-world experience".
• I don't know about you, but I've experienced more politics in the OSS world than in the business world. Why? Everyone is doing it for love, not money. Doing something for money means that you're more willing to eat crow and shut up. If you're doing it for love, you're more passionate about the topic. This means that module maintainers have to be approached gingerly if you're going to get major work done. Getting reworks done shows some good political acumen.