The ultimate website for packing well is OneBag.com. Created 11 years ago, this site encourages people to travel with only one bag, as its name suggests. But even travelers who carry several bags will find useful packing tips on this site.
A few years ago, I met OneBag.com's creator, Doug Dyment. He's a technical marketer in San Francisco who uses the site to share his thoughts on the the superiority of traveling light. He's refined his strategies over the years as he's learned from hundreds of fellow travelers who have e-mailed him.
Dyment, one of the most gentlemanly fellows I've ever met, has a fantastic trick for preventing your clothes from becoming wrinkled. As he says, "The common practice of individually folding items of clothing, then piling them atop one another, is just about the worst thing you can do from a packing perspective." His trick is "bundle wrapping" instead. His explanation is better than any I can give, so I encourage you to visit his site.