I have a friend who wrote a open source library that is very popular. It is a testing framework that is very well known from within the Python community. This guy was a coworker of mine a few years ago. When he sent a resume to the company, they pretty much hired him on the spot because of the fact that he was the author of [famous open source project]. He didn't go through any interview process, at least not in the tedious FizzBuzz / "what are your biggest strengths and biggest weaknesses" sense.
Thats why I do open source. Hopefully one day I'll get lucky and one of my projects will catch on and become very popular. When that happens, I have guaranteed employment pretty much for the rest of my life. Although, only like 1% of all open source developers are lucky enough to have a project with enough "cred" to be in that position. It mostly has to do with luck. There are tons of popular projects that suck (PHP), and tons of projects that are amazingly written, but not popular.
You don't really need to be author of a "famous" library. Just having a body of high quality code on display (even if not used by a lot of people), sets you apart from the majority of programmers.
In my experience, few people cares about your open source work unless its something they have heard of. _I_ may care. _You_ may care. But most people don't. I have a "large body of code on display" in my github, but I know for a fact that no one ever looks at it.
Thats why I do open source. Hopefully one day I'll get lucky and one of my projects will catch on and become very popular. When that happens, I have guaranteed employment pretty much for the rest of my life. Although, only like 1% of all open source developers are lucky enough to have a project with enough "cred" to be in that position. It mostly has to do with luck. There are tons of popular projects that suck (PHP), and tons of projects that are amazingly written, but not popular.