hdiff shows you the changes between different releases of a package. Use this web interface or the bookmarklet below when browsing hackage.
hdiff
(drag to your bookmarks toolbar to use)
Browse packages

hdiff is also a complete hackage mirror. Add the following line to your cabal config file to use hdiff as a package source:

remote-repo: hdiff.luite.com:http://hdiff.luite.com/packages/archive

Latest updates: (updated every 10 minutes)
contact me: Luite Stegeman <stegeman@gmail.com>