Buses are a good way to travel as they occur frequently and are cost effective. Most buses in Cambridge are operated by Stagecoach (Citi), where you can buy a ticket from the driver. A Dayrider ticket is valid for unlimited travel on Stagecoach buses for one day. Other options include a Megarider ticket, which provides unlimited travel on Citi buses for seven days. Most bus stops have electric signs that report when the bus will arrive. The main bus station is on Drummer Street, in the centre of Cambridge.
For University employees and students with a University card you can ride the UNI 4 bus for a significantly reduced fair. These buses run across the city every 20 minutes.
You can find further information on local bus routes here: http://www.cambridgeshire.gov.uk/transport/around/buses/