It's been discussed before, to include on my blog (http://jolly-green-giant.blogspot.com/2009/04/lightweight-gear-tips.html), but I wanted to briefly mention a new tool I found to dig a cat hole. Yes, we're going to talk about taking a crap in the woods boys and girls.
As many of you likely know by now, my personal belief is that going lightweight doesn't mean being personally stupid nor irresponsible towards the environment. I feel it is the intrinsic obligation, duty, and responsibility of a backpacker to be a good steward of the environment even if it means taking a few extra steps (or extra pieces of undesired gear) to keep nature as pristine (and ecologically safe) as possible. This includes when "self-evacuating".
So yes, you can dig a hole with a stick or a rock and leave a more conventional shovel or digging tool at home. To me though, I'm not really interested in playing a game of beat-the-clock with an old school digging stick which may or may not be immediately capable of digging a decent hole 6-8" down. If it fails, all you do is spoil the environment and likely cause grief for the flora and fauna of the area. So with that, I support bringing some kind of digging utility.
As with anything carried by a lightweight backpacker, my goal is to find the lightest option if I feel I need to carry it. In the past, the most responsible and lightest hole-digging tool I used was the Montbell Handy Scoop (1.4 oz, 6.5", $8), which I still think is a great tool. Other options were either too bulky or I just couldn't dig a decent hole with them.
Many UL'ers have suggested using a tent stake, like the MSR Groundhog or a winter tent stake which has a much more robust scoop. Well, I've found it is tough to dig a good hole with the Groundhog principally because it is three-sided and a winter tent stake is just too big and heavy.
I happened to be in Eastern Mountain Sports (EMS) the other day, just snooping around, and came across a brand of tent stake I hadn't heard of before - "DAC". EMS sold a 7" "V" tent aluminum tent stake by DAC which was $1.30 (http://www.ems.com/product/index.jsp?productID=3655464) for a variety of colors and weighed a mere .5 ounces (14 grams). The length is a little longer than similar stakes and the "V" is a little wider. As a result, I've had some success digging holes in my backyard with it and plan to use it as a replacement for my Montbell Handy Scoop which is substantially heavier. And as a nice expected bonus, I can use it as a tent stake in a pinch (one which would likely need to be beaten into place with a rock unless the ground is very soft).
If you're looking for a digging tool, give it a shot. I decided to tie a piece of shock (elastic) cord to the end of mine. In the past, I kept my digging tool in a plastic bag with my toilet paper merely to keep it all together, but the tool was usually dirty and soiled (or stabbed) the toilet paper. With the shock cord, I can put the toilet paper in a plastic bag and cinch the stake around it on the outside with the shock cord to keep it all together without spoiling the toilet paper. And yes, I carry toilet paper.....most of the time. What can I say, my butt prefers it over a nice abrasive pine cone.