If you're an Ableton user, I wrote a script that will create and install instruments from the CC-licensed Philharmonia Orchestra samples:

https://github.com/Miserlou/ADGMaker

There exists a rather extensive free orchestral library for Korg Kronos.

http://www.korgforums.com/forum/phpBB2/viewtopic.php?t=88665

The post says it is spliced from Sonatina Symphonic Orchestra samples and Free HQ Orchestra Soundfonts[1], so they must be pretty good. There are individual instruments, choral arrangements and orchestra sections there.

1 - https://sso.mattiaswestlund.net/

2 - http://the-filmmusic-group.deviantart.com/journal/Free-HQ-Or...

You've probably found it already, but you might also be interested in the Virtual Playing Orchestra, which is a compilation of various Creative Commons orchestra samples. It sounds a bit "General MIDI", but if you dive into the samples there are individual instruments and some usable stuff.

http://virtualplaying.com/virtual-playing-orchestra/