Here are some good articles on using CMOS chips in stompboxes.
http://www.parasitstudio.se/building-blog/cmos-workshop-part-1
http://www.parasitstudio.se/building-blog/cmos-workshop-part-2-square-wave-fuzz
http://www.parasitstudio.se/building-blog/cmos-workshop-part-3-octave-down