If you want to get involved in the local community, meet people or have a skill you would like to offer, you might consider volunteering at one of the many local charities or community groups active in Oxford. Although volunteering is unpaid, some opportunities offer skills training or managerial experience which can be valuable on your CV (resumé).
You can find information about volunteering opportunities on the government website, or search the Do-it database.
The University Newcomers' Club run regular sessions on volunteering and publicise opportunities through their email lists.
Note for visa holders: if your visa has any work restrictions, you may not be eligible for voluntary work.