A friend of mine is currently hiking the Pacific Crest Trail and another friend has done the Appalachian Trail twice. What I have learned living vicariously through their adventures is that in thru-hiking, every ounce matters.
One key area to cut down on in size and weight is cooking (pot, stove, fuel). Alcohol stoves are a very popular way of doing this today as they weigh a mere couple of ounces and the alcohol fuel can be found almost anywhere along the trail.
The debate on the optimum stove design and fuel combination rages on. There is the tried and tested Roy Robinson homemade cat food stove, or Pepsi and beer can stoves; the list goes on.
Vargo Outdoors, originally started by Brian Vargo as a site to discuss ultralight backpacking techniques, is now an ecommerce shop selling all the gear one might need for their thru-hike adventure. Vargo has also created their own Titanium line including alcohol stoves, cookwear and tent stakes as well as a DriSeal dry bag/pack line. Check out Brian's intro to Vargo above (BTW- love the dog shake cameo around 1:38).