From the homepage:
The 1.5 release of Nutch is now available. This release includes several improvements including upgrades of several major components including Tika 1.1 and Hadoop 1.0.0, improvements to LinkRank and WebGraph elements as well as a number of new plugins covering blacklisting, filtering and parsing to name a few. Please see the list of changes made in this version for a full breakdown of the 50 odd improvements the release boasts. The release is available here.
If you are looking for documentation, may I suggest the Nutch wiki?