We had a thread on this automatic packing list generator a while back, but that site no longer works. I just found this one:
http://www.travelindependent.info/
It is really comprehensive and one thing I really like is that it has a lot of recommendations based on the latest materials and gear innovations available (like suggesting underwear made out of a wicking polyester fabric because they stay fresher and are easy to clean, socks with anti-microbial fibers to minimize smell, collapsable water bottles, etc)
When I'm ready for my longer trip I'll definitely need to buy some of this stuff!