Daisy is spot on about the Thermarest Prolite series (or, if you need a bit more comfort, the Prolite Plus - if you have a nearby store, go lay down on one for at least 10 minutes.) They are a cost-effective solution at a very tolerable weight. I used them with no complaints for about 10 years, and replaced them with a NeoAir eventually. The pad is probably an easy, 1-pound-saved fix at a reasonable cost.

Before discussing your sleeping bag, we need to know the temperature rating. 36 ounces isn't hatefully heavy for a 20-degree bag. If it is rated that low, you'll probably save at most half a pound with a top-line bag - not enough to make it a priority, and it can go to the bottom of the list. If it's a 40-degree bag, you'll definitely want to replace it for the warmth - but you'll still only save about half a pound with a top-line 20 degree bag.

The tent should go to the top of the list. You can easily drop 2 pounds here with a double wall tent like a Big Agnes Copper Spur UL2 or MSR Hubba NX2. You can save 3 pounds with something like the Big Agnes Scout or MSR Flylite (due out in another month.) And, naturallly, the TarpTents will probably maximize weight savings. The single-wall tents may present some condensation problems, depending on the conditions in which you'll use it. If it doesn, then a simple silnylon tarp and groundcloth might be a solution, too. Again, without more information on how you'll use it, it's a little tough to make specific recommnedations, though the foregoing may point you in the right direction(s).

For sleeping bags, the Western Mountaineering Megalite and/or Mitylite might work. Neither are true mummy bags, and the Mitylite is nearly rectangular. Each weighs about a pound and a half (and the MityLite can be used as a quilt. This year, I'm experimenting with two Thermarest bags: the Antares and the Auriga (a quilt). Both are a bit roomier, and so far the Antares has kept me warm in shorts and a T-shirt on a 28-degree night. There are other quilt options in the Thermarest line. There are also warmer quilts available from other manufacturers that receive high ratings (other posters can help: Jacks R Better? Feathered Friends? others?)

Now, tell us about your trail kitchen and eating habits. Sometimes, that's a no-cost weight loss just by rethinking your menus and meal preparation process.