I recently attended a Digital Scholarship workshop at the British Library. One thing that was discussed was the challenges of preserving access to digital content such as websites which may be short term or disappear without being captured eg an election website. In an attempt to address this, since 2004, thousands of UK websites have been collected by the UK Web Archive from the British Library and the Archive is growing.
“Here you can see how sites have changed over time, locate information no longer available on the live Web and observe the unfolding history of a spectrum of UK activities represented online. Sites that no longer exist elsewhere are found here and those yet to be archived can be saved for the future by nominating them.
The Archive contains sites that reflect the rich diversity of lives and interests throughout the UK. Search is by Title of Website, Full Text or URL, or browse by Subject, Special Collection or Alphabetical List.”
There is also a: UK Web Archive blog
This search is a visual representation of the occurance of search terms over a period of time eg compare David Cameron and Ed Miliband. This could be used to assess online popularity of a public figure at a given time for example.