I can second the suggestion of getting in touch with the Red Cross. I've been volunteering for over a year now with my local chapter (Zurich) and they have different types of work depending on your particular aptitude and how much time you've got to give. For example, they're always looking for drivers to ferry older or disabled people to doctors' appointments and the like (they comp your expenses and I think even take care of insurance), and also have a type of Big Brother/Big Sister program for kids new to Switzerland, but there are lots of different things to do. They are also, at least in my experience, very good with getting you up and running with whatever you end up doing - it might include an informal training - and very my-door-is-always-open-for-you kind of people to work for (volunteering is work too).
If you like, I can put you in touch with the volunteer coordinator for Zurich (private message me if you're interested).