It might feel like overkill, but this super condensed way of folding jeans allows you to store 'em horizontally and pack more pants into each drawer. Get the tutorial at What Wit » - GoodHousekeeping.com
I love this system of "filing" clothes. I do it for my shirts, PJs and jeans. Never thought about doing this for undergarments, but I think I'll start doing it for them, too! Click for a summary of how to fold tons o' stuff!