Agree completely. Find a FOSS project that uses the same technologies as you'd like to use in your 9-5 job, and get stuck in. It (generally) costs nothing more than your own time.
Given a choice between 2 programmers with similar skillsets and experience, I'd be inclined to go with the guy who's got FOSS coding experience in his background. The implication is that you're prepared to put your code out there for peer review (which takes some guts), and you're prepared to write code to scratch your own personal itches. Both of those demonstrate qualities in the people I'd want to work for me.
Imagination is more important than knowledge. -- Albert Einstein