All these companies have websites so you can decide which one you think is best. I particularly liked Cambridge Punting Tours description of the "Punt Wars" that exist between the various companies.
The Granta Punt Hire Company
Cambridge Chauffeur Punts
Cambridge Punting Tours
Sudamores's website is not currently working but you can ring them on 01223 359750.
If you don't want to pre-book then you can hire punts from Silver Street or Quayside by Magdalene Bridge.
Wikipedia has an article which tells you pretty much everything you could ever want to know about punting and punts- at the bottom of the article there is a link to St John's College Punting Society which has a very good map which tells you what you can see as you punt up stream. Unfortunately some of their other pages did not seem to work.
...and here's a YouTube video of some people punting.
