I recently stumbled on this free orchestral sample library by Mattias Westlund called Sonatina Symphonic Orchestra. I have to say that some of the sounds challenge a few of the commercial orchestral sample libraries!
These will nicely spice up your electronic tracks and I highly recommended them.
Sonatina Symphonic Orchestra is a free orchestral sample library. While not as advanced or ambitious in scope as commercial offerings, SSO contains all the basic building blocks for creating real virtual orchestrations. It’s primarily aimed at beginners, but also more experienced composers looking for something lightweight and/or portable might find it useful.
The SSO samples are stereo, 16 bit, 44kHz. Melodic instruments and chromatic percussion are sampled in minor 3rds. Staccato/pizzicato patches have 2x round-robin. All samples have varying amounts of stage ambiance, depending on their front-to-back placement, but in addition to that, a good hall reverb is a must.
The sounds are in .sfz format, so the best way to start playing with them is to download and install the free SFZ Player by Plogue.
Licensing: SSO is a free (as in speech, and beer) library released under the Creative Commons Sampling Plus 1.0 license.