Don't go out of your way, but if you have any of this stuff lying around and you're coming to visit, I'd love to have it. In some cases I would even pay for it.
Clay
I still don't have enough for the cob walls of the cabin.
Coarse Gravel
For wall foundations.
Red Lava Rock
Little pieces for ground insulation, and big pieces for embedding in cob walls.
Vermiculite / Perlite / Pumice
Insulation for rocket stoves, or if I get enough, for the cabin walls, or for garden soil.
Straw Bales
Ideally winter wheat. This is for cob, and also for urine composting.
55 Gallon Metal Barrels
With lids, I can use them for storage, and without, I can use them for rocket mass heaters.
15-20 Gallon Metal Barrels
Ideally, with a lid that lets a little air in, as the intake for a rocket heater.
Water Heater Tank
Also for rocket stoves, good for the wall that goes inside the big barrel.
Bricks and Firebricks
Again, for rocket stoves.
Heavy steel pipe
Five or four inch, for the riser in an experimental low-diameter rocket mass heater. At least three feet long.
Stovepipe
Eight, five, or four inch.
Unglazed Clay Pots, whole or broken
I can use the broken ones for Terra Preta, and the whole ones can make evaporating refrigerators.
Plastic Five Gallon Buckets
Best if they've held food and not toxic stuff. No lids necessary.
Spray bottles
Either direct stream or mist. There are a lot of these around but I'm constantly wearing them out.
One Gallon Glass Bottles
Can't have too many.
Sawdust
For composting toilets, trails, insulation. Can't have too much! Partly composted is fine, but I don't want any from treated lumber.
Tarps
At least 6x8, for covering stuff and mixing cob.
Double-paned windows
Either small ones that open, or big sliding glass doors which I can use as tall windows.
Milk Crates
As many uses in the woods as in the city.
Metal Bathtub
I eventually want to build a bathhouse with a tub heated by a fire. I've heard different things about whether a cast iron or a steel tub would be better, but I think I can work with either one.
Metal Roofing
I have enough for the cabin, but I could always use more for extra structures.