There may be others lurking (and there are certainly some officers lurking) but the following city councillors who are currently active on cam.misc: Colin Rosenstiel, Tim Ward, Rhodri James, and Alan Levy.
There is one county councillor (although from the city) who posts sometimes: Rupert Moss-Eccardt
Just outside the city Denis Payne is a chairman of Impington Parish Council, Barry Jefferson is a parish councillor in Milton and Douglas de Lacey is both a parish councillor in Girton and also one of their district councillors. Jon Green is a parish councillor for Fen Ditton.
All councillors (other than parish councillors) now have email through their authorities - although some get it printed and posted to them so it may take longer to reach them.
You can find out who your councillor is and whether they have an email address by looking at the appropriate Web pages on their respective Web sites. The City Council, South Cambridgeshire District Council and the County Council all provide lists by name and ward.