The fact that you have to even ask this question (I've been in same boat) is evidence that traditional resumes and hiring mindsets are broken and archaic. The "X years of experience in Y" concept being probably the poster boy. Because what does X mean? Is X years by Bob equivalent to X years by Steve? What if X years in Y yields greater mastery than A years in B, because the former occurred later in their career, or because B was more difficult?
For example, I wrote a lot of C code in the 90's, but never "professionally" and so I periodically encounter recruiters whose brain just implodes at that concept. How could I possibly know C if I never did it for a paycheck? Is he lying? Talk about an insane world view.
I'd prefer seeing it under a "Personal Projects" section. It's more impressive when you do cool stuff without a paycheck attached. If there isn't enough space to get everything across, list one or two projects and link to a web page that shows the rest. Here's the portfolio page of someone I actually ended up hiring: http://crccheck.com/portfolio
For example, I wrote a lot of C code in the 90's, but never "professionally" and so I periodically encounter recruiters whose brain just implodes at that concept. How could I possibly know C if I never did it for a paycheck? Is he lying? Talk about an insane world view.