I've actually just recently done fairly extensive research on weather balloon technology for lofting wireless gear and I can tell you that the "lift" capacity of a standard 3' weather baloon is marginal under the best of circumstances (same for 6' and 18' which go up in cubic volume eponentially). If you attach some sort of lift generating structure such as wings and tail (ala assisted kite/ballloon hybrid "Platform") then you can get decent capacity of lift if the wind is blowing. But we are talking ounces. And the larger a ballon gets the more helium or other LTA gas is used and price goes up.

Now, in a field expedient sort of way, the ONLY rational use I could think of to carry a cylinder of Helium and a few weather baloons would be for signaling. And even then, you really need an anchor of some sort. Even monofilament has some weight, so in all but the most forgiving of circumstances, this is a likely a no-go. But I can see a 3' orange balloon with a few hundred feet of mono as a decent signal.

For those interested, I'm working on a lofted 802.11g (or MAX when it comes) wireless solution where I strip off all components of a router except an antenna and power it using super-thin leads from the ground. Think Power Over Ethernet, but with 2 wires and thin resin shielding. Why not just float an antenna instead of a router+antenna? Well, I'll leave that to the HAM crowd here, but let's just say that long copper cables aren't necessarily conducive to antenna function and signal loss.

Anyway, even then, under pristine conditions with tiny load and lifting structure and mild wind (enough to lift without shredding) and you just MIGHT get enough to carry up a few extra oz. of equipment on top of the cable to power it.

The wind resistance you pick up from a balloon will far outclass the reduction in weight if you are dragging it along. Plus, who's carrying Helium into the woods besides scientists?

And if you are talking hot air balloons, well, good luck packing those on a hike.