I have done all sorts from residentials with the severely disabled for holidays and respite (was Winged Fellowship, now Vitalise), in the day unit of a local hospice, Women's Aid, RWVS Contact Centres, local deaf club (I learnt some sign language too), student tutoring a blind girl in mainstream school (and helping out with other children with learning difficulties) and more ad hoc stuff like helping out at events and lots of charity work from collecting to helping run or help generally at events.
I did some BTCV work as well doing day events helping with conservation work such as clearing areas, dry stone walling etc...
I did a couple of days work at a place which helps people who have been homeless or had drug problems, just come out of jail etc... get back on their feet with training and life skills so something like that could be possible.
There are so many possibilities - do you have a large local park where they have volunteers who help keep it nice (my local one does and has sessions at least once a month).
Some places have local volunteer bureaus - you could try and find one of them?
Why not see if you could organise something yourself? See if you could find something that needs doing and see if there is any way of organising it such as clearing an area of litter or getting it tidied up, or fundraising for a local project by running events (could be very social) and maybe something where others can volunteer their time such as doing up a local centre which needs painting and sprucing up so better for the community to use (baby/toddler groups, scouts, brownies, guides, Weightwatchers, village meetings etc..., mind you could be a minefield these days with the compensation culture and such but the council may be able to advise and possibly know about grants and such.