Let's see. My first job, I got when a job offer fell through, and the hiring manager told me about this other company that had a similar job open. My second job was after reading about a startup launching and emailing them. My third was when I joined former co-workers. My fourth was when I contacted people I used to work with.

I guess you can call it mostly networking. Obviously, networking works better as you gain more experience, start knowning more people and get better technically.