Look for volunteering

Hello!
In order to gain more experience, I look for some company or organization that need web application. I will do voluntary work. I have little enough time. So, I look for small-scale, part-time and short-term collaboration.
I've already used : PHP (with CodeIgniter and Laravel), Python (Django/ Pyramid), .Net (WPF), SQL, some SPA with Vue.js and React.
Do you have any tips? Thank you very much.