Where is a good collection of freely licensed instrument .wav samples?

I require full samples for a variety of instruments. One such site that provides this resource (http://theremin.music.uiowa.edu/MIS.html) is good, but there aren't enough non-classical instruments (e.g. steel guitar, drums).

I need a different resource that provides instrument samples such as ones the MIDI specification supports.

Side note: I only require middle C samples for each instrument.

What is a WAV sample?

The WAV audio format was developed by Microsoft and has become one of the primary formats of uncompressed audio. It stores audio at about 10 MB per minute at a 44.1 kHz sample rate using stereo 16-bit samples. The WAV format is by definition, the highest quality 16-bit audio format.

One thing you could try is to search around for free Reason Refills, and also look for Refill Unpackers to get at the samples contained within the refill. Just make sure that you are allowed to do so under the terms of the refill license.

Also, check out PrimeLoops and Freesound