I have just returned from Prague and I would like to advise fellow travellers who may be thinking of going to Prague of the excellent service we received from Scott (American chap) at http://www.prague-airport-shuttle.com/
He was friendly, helpful (advising the best time to see the Charles Bridge), good cheap bars...and they were! Plus recommendations of restaurants, which again were great. We also received simple advice of how not to get 'stung' to a degree on beer or food which was helpful in our trip.
Hope this helps.