What have you done for me lately?
- Janet Jackson
It used to be that only artists or architects had portfolios - large, briefcase-like things they'd carry around that would showcase their previous work. So that they could land their next work.
But with the Internet, and word processors, and public code repos, video sharing sites, etc, we all have this giant platform available to us. We can set up our own portfolio regardless of discipline. It's a little easier for, say, software developers because anyone with a web browser can see the website you built. But that doesn't mean you can't run a blog, keep a list of talks you've given or contributions to your community (both your neighborhood and professional community). What about book notes? You are reading books and taking your own notes on them, right?
To be clear, this is not your resume. That's a list of things you did because it was part of your job. I'm talking about things you did because you wanted to do them or they needed to be done. What initiative did you take? What did you do, that was valuable, and no on asked you to do it?
Your portfolio is what you use to show the world "This is what I can do for you". It shows you have value. It shows you're worth taking a risk on. Make sure it's healthy.