This whole site is dedicated to lightweight backpacking. Go to the Home Page and start with the articles and gear lists, then come back to the forums and start reading through them. Lightweight backpacking is not just about paring down the weight of individual pieces, although that is part of it, but putting together a system for each task-shelter, sleeping, cooking, survival, clothing.

Before buying a lot of new gear, next time you go camping, lay out all your gear, put half of it back in the closet and the rest in your pack. And no, I'm not kidding.