Huntingdonshire District Council runs a similar service for accommodation in their area. Go to:
Adverts for accommodation to let / wanted in Cambridge are also carried by the following sites:
Agencies offer a choice of services, for example a management service which can be essential when the landlord lives a long way away and cannot turn out in the middle of the night to fix a burst pipe themselves, and make a charge, which means that the tenant pays more rent and the landlord receives less rent. Agencies also, potentially, give both parties someone to sue if anything goes wrong! - which is of course part of what you are paying for. If you don't want to pay part of your rent to an agency and are sure you can manage all the legalities and technicalities of managing your property yourself (not actually terribly difficult - if I've got time I may give advice on request, but I'm not a lawyer or consultant and will accept absolutely no responsibility at all whatsoever for any advice I give) you may prefer to advertise (free) directly on the Cambridge Accommodation Notice Board.
Note that I do not endorse or recommend any of the agencies listed here - it is up to you to decide whether to do business with them. Personally I wouldn't deal with any agency that tried to charge tenants a fee (is that actually legal??) but that's up to you.
If you prefer to use an agency the following have asked me to provide links, which I am happy to do (just ask):
These sites have references to accommodation information.
If you are buying or selling, rather than renting, here are some links to estate agents' sites and other property advertising sites (again, if you want a link here, just ask).
The following newsgroups sometimes carry accommodation advertisements.