For those hikers new to ultralight, here are a few links that I found very helpful in getting background info about the philosophy:

http://www.adventurealan.com/

In particular, his description of his 2.4-lbs Full Skin-Out Base Weight really changed my paradigms regarding hiking gear: http://www.adventurealan.com/2-4_index.htm  That picture is him wearing his sleeping bag as a poncho.  Yes, wearing his sleeping bag.  Hard core.

http://www.ultralightbackpacker.com/

"Ultralight" Joe explains his progression from heavy to light, and the attendant benefits.

http://www.backpackinglight.com/

The ultralight backpacking zine, where the devoted meet and mingle.  Unfortunately, some of the content requires subscription, but I've managed to get a lot out of the site even without that content.

http://www.southwestguidebooks.com/desert_gear.htm

The top link in google when you search for "ultralight hiking desert".  For the "Shvilistim" (Israel Trail hikers), this is a particularly relevant area (thank you, Negev Desert).  Most of the ultralight concepts were developed in the water-plentiful deciduous forests of North America, so the thinking takes some conversion to be relevant to new biomes.  

http://www.trailcooking.com/

For those who have gone as far as getting involved in Freezer Bag Cooking, which they also describe on the Southwest Guide Books site.  

http://www.andrewskurka.com/advice/technique/fastthruhike.php

This was an article that inspired my philosophy regarding the Israel Trail (and the rest of the site has some good stuff, too).  As he is quick to point out, the "Fast-packing" ethos is not for everyone.

Since this is now a new thread, feel free to also contribute links that you have found helpful.