Kenneth King is teaching an online course for Craftsy.com on how to make a pattern from your favorite jeans.  I watched the previews and it looks very well done.  I've taken a class from Kenneth in person and he is a good instuctor. Hmmm I have a pair of favorite jeans.  It would be fun to duplicate them in red denim, or aquamarine, or...

http://www.craftsy.com/class/Jean-ius-Reverse-Engineer-Your-Favorite-Fit/60