Paul Bausch wanted a TouchGraph browser for Amazon's new citations feature, so I couldn't resist ...
Use this ->AmazonCitationsGraph<- bookmarklet to launch it from any Amazon.com page (or in fact any page that displays the ISBN of a book in the URL) - like this example page, or follow this direct link to the graph if you just want to see how it works.
Double clicking on any of the nodes will load a new set of books which either cite or are cited by the selected book - in other words, opening up new nodes moves both backwards and forwards in time through citations (at the moment, no differentiation is made between 'cited' and 'cited by' links.
Clicking on the 'info' box will open a window with a link back to Amazon.com, from where you can read more information.
Note: Safari seems to scramble the backslashes in the bookmarklet, so you might need to copy it from another browser.