Hey James
There are two that can be used Ridgeline which is the original NMS from Extreme that came after EPICenter. It can manage all of the XOS switches but is not a network wide NMS. As Aloeffle mentioned NetSight is the new NSM for all of Extreme products. NetSight is from our Enterasys merger and is a true NMS that can manage any device.
Most of the features from Ridgeline will be in NetSight with version 6.2 which is due out in Q1 Calendar year. 6.1 which is out right now provides a great stable platform for managing the network with Alarms, Config Backups, SNMP management etc.
I hope that helps
P