I hate pottering like cattle in a mass behind a guide.
Two young entrepreneurial guys have a solution. Recently they set up a website, Audio City Tours, where, against a small fee, you can download an MP3 file, that guides your walk through Amsterdam. Two tours are available for the moment: An Old Amsterdam Tour and a Rembrandt Tour.
A Salzburg Mozart Tour is in preparation. They have to be fast with their Mozart tours, as the Austrian site Calling Mozart [url deleted as the site dissappeared since, ed.], set up by the Austrian State Radio ORF, provides a series of free tours in Vienna along various points of interest connected with Mozart.
In the UK it exists already under the name Tourist Tracks with tours in Bath, Brighton, Cambridge, London en Oxford. I also found one for Gloucestershire [url deleted as the site dissappeared since, ed.].
Update: They closed in the meantime.
Last Update January 2017