Octave 5.1.0 is the current stable release. The source distribution as well as a Windows binary installer are available for download.
The first release candidate for Octave 4.2 is available for testing. The source distribution and Windows binary installer can be downloaded here.
There may be an OctConf 2017, an announcement will be made when a time and place has been chosen.
For details on previous conferences, see Category:OctConf.