Cambridge National Trust Volunteers - Sundays - local NT sites such as Wimpole Estate & Anglesey Abbey
Weekly Tuesday Conservation Group - Tuesdays - Cambridge City LNR sites
Wildlife Trust Cambridgeshire Midweek Group - Wednesdays
For details of the Tuesday and Wednesday groups see the BCN Wildlife Trust work parties page. It also lists groups that work at specific WT sites.
naturenet Conservation Volunteer Groups - a long list of groups around the country
conservationgroups.org.uk - A directory of conservation groups
Natural History Museum - Nature Groups Near You
The Conservation Volunteers - National organisation - used to be called BTCV
CPERC - local records centre
Cambridge Conservation Forum - group of local, national & international organisations in Cambridge