I haven’t volunteered in the library sector but I have volunteered at festivals and I volunteered at a local Oxford museum for about a year. I volunteered at the museum on Saturdays whilst working at 9-5 Monday – Friday. I had tow reasons for doing this. One being that I wanted to understand more about the workings of museums and gain some experience there. I have previously considered working in museums, but and noticed that all job descriptions required experience and I thought in that case the only way to get experience is to volunteer! I also just felt I should be doing something with my spare time and it was a museum I had always enjoyed visiting.
Whist volunteering at the museum I got to work with some really interesting people and did get to learn a lot about the ‘behind the scene of the museum. I was already in paid, full-time employment, but a lot of the volunteers there were otherwise unemployed or giving up their free time in retirement and I know the museum sent volunteers on courses etc where they could to build up their CVs and gain more skills. I think this was really good for both volunteers and the museum.
I know a couple of people who have volunteered or done intern ships at the places and eventually been offered a job there, so I think it does go some way to opening up opportunities to people and is certainly something I would consider doing again.