There are a number of expensive hotels around in Cambridge which can look after themselves but the question of good cheap guesthouse/B&B in the city suitable for visitors has come up.
The Assissi, on Cherry Hinton Road was recommended by two posters one of whom commented “nice rooms and very hospitable owners”. The Hills Guest House is “also very good, very 'modern' decor - somewhat smaller (2 single, 1 twin and 2 double rooms”.
One poster suggested The Grafton Hotel in Newmarket Road, near the junction with Barnwell Road. They said it “had a couple of weak points when I stayed there last April  but it has had a major refurbishment since then. The new Italian Restaurant on the ground floor does excellent food too.”.
The Dresden Villa on Cherry Hinton Road (the end near the station) has been used repeatedly by another poster's parents and others had sent relatives without complaint to the Bridge at Clayhith and Brooklands or Fairways near the top of Cherry Hinton road.
There's a long list of reasonably priced places to stay available here.