I need recommendations for places I can add a volunteer project for a portfolio case study

Hi, I’m researching different ways to add a real world collaborative case study to my portfolio. I want to show in a case study how I collaborated, as a UX Designer, with other designers, PM’s, and developers. The places I’ve been referred to are UX Rescue, Hack for LA and Catchafire. I would like to hear if anyone has any experience with these or can recommend others?