We have a basic snugli framed backpack type carrier that we really like. Even with the frame it is pretty light, and it has a nice roomy pocket. The best part about it is that it has a shade. I went up the side of a mountain (well a Georgia mountain) when DS was about 15 months and had no problems. Dh and I both use it, and it is easy to adjust. It is also nice, because you can set it on the ground with the baby in it if you need a little break.
I also have a hip carrier (Playtex hip hammock) that I love. It got really mixed reviews though, so I would say to go to BabiesRUs and try it for a little while before you buy it. From the reviews, it seemed that if you had a certain body type you loved it, if not, it started to hurt. Dh does not like this as much as I do, but he's a guy so he doesn't have hips to begin with.
I looked on babies r us, and they have this frame carrier that connects to a stroller frame. I know nothing about it, but I like the idea.