Solaris within Oracle is as good as dead from the latest reports. However, Illumos is a Solaris descendant that is very much alive. It has all the good systems stuff that came out of Sun (zones, ZFS, DTrace) and is backed by Joyent (now part of Samsung).

There's also FreeBSD jails that can be used to contain applications. I'm not sure about the timeline, but I think jails came first. Sun engineers wanted to achieve the same so they ported the same technology over to Solaris.