This page has links to some of my favorite royalty-free sample and loop banks available on the web. Anything hosted on my site is abandonware.
Voxengo Free Reverb Impulse Responses – If you use convolution reverbs at all, you’ll love these free impulses. They sound excellent and are entirely usable.
Impact Soundworks Acoustic Revolutions, Vol. 1 – Acoustic guitar loops for the aspiring songwriter. Very usable, and quite inexpensive.