Oracle closed OpenSolaris development and went closed source again in 2010. Before this happened the illumos (yes it's lower case i) project had been announced by internal developers to help get some of the closed source parts of OpenSolaris to be rewritten as open source. After OpenSolaris died, the illumos project forked the last version of OpenSolaris.
For a really really nice history on this and on illumos see the video below.
illumos now has several distros that you'll probably be interested in.
NexentaStor and napp-it would be what you're looking for if you want some ZFS storage on a NAS.
OpenIndiana is what you want to use if you're a masochist that wants Solaris on your desktop.
OmniOS would be an all-round replacment for your Solaris server installation.
Illumian is an all-round server OS but with dpkg/apt from Debian.
SmartOS is what you want if you want to run a bunch of Zones and KVM guests on your server.