The Bitcoin Core developers have a desire to do a mostly bug-fix, cleanup
and translation update release in v0.9.2 a few weeks from now.  You do not
need to be a developer to help!  With these unofficial nightly builds,
power users can more easily aid in testing of the master branch which will
help to find bugs and polish things up faster.  Additionally translators
can more easily run the latest code and see what strings need to be
translated as we rapidly approach the next stable release.

https://bitcointalk.org/index.php?topic=571414.0
Read more details here.

Warren Togami