Some time ago, I got into building guitar effect pedals. It's a great hobby and I've actually used a lot of the boxes I've built. For over two years I've been looking for the Stompbox Cookbook at a reasonable price. It went out of print a while back and shows up occasionally on Amazon or Ebay for 2 or 3 or $400. After using Google book search I got a list of libraries that had the book in stock and participated in the interlibrary loan program. One week later I was able to pick the book up for free at my local library! I have it for a couple weeks and the only drawback is copying the book is illegal. Nudge, nudge, wink, wink.
