OAD – The Office of Astronomy for Development are always looking for volunteers, on projects that you can do online.
IDA – Perhaps you might like to become an Advocate for the International Dark-Sky Association, where you will have access to monthly training relating to light pollution and dark sky conservation.
IAPS – The International Association for Physics Students has a lot of opportunities, from advocacy to outreach. A great way to get some hands-on experience.
ISEC – The International Science Engagement Challenge are always on the look out for mentors for their summer camp (happening online this year).
VIS – I volunteered at the Mauna Kea Visitor Information Station a couple of years ago and it will remain one of my fondest memories for as long as I live. They really care about their volunteers, whether about teaching them how to use some super duper fancy telescopes, or how the ancient Polynesians traversed the Pacific Ocean using only the stars to guide them. The island itself has so much to offer, from beaches to lava to jungle, it’s impossible to ever experience everything.
ASP – If you’re interested in science education, I’d definitely get in touch with the Astronomical Society of the Pacific.
Kitt Peak – The Kitt Peak Visitor Centre has a Docent Program in Southern Arizona.
SDSO – The Scottish Dark Sky Observatory in Galloway is always happy to receive volunteers.
Kielder – The Kielder Observatory in Northumberland is always looking for volunteers.
Summer Science Exhibition – Volunteer with the prestigious Royal Society in London.
RMG – There are sometimes opportunities to volunteer at the Royal Observatory Greenwich. They also have work experience available during the summer.
There is no limit when it comes to possibilities of volunteering. And it is in no way a derogatory experience if you end up doing something a little unusual. Don’t feel like you have to do a summer research project, just because everyone else is doing one! For example, you could write to your local Planetarium, Science Museum, Observatory… and ask if there are any volunteering opportunities available. When I went to Hawaii I ventured out in the hopes of doing as many different volunteering roles as possible, and ended up doing 4 at once! It’s also possible to find funding to help you, like the Physics department at your University for example, or an Astronomical Society/Association. People want to help you volunteer for something that you feel is important and worthwhile!