Barrels can be used for storing grain/feed after the tops have been cut out. Making a vermine resistant top is the key for their use.
Barrels can also be "dug in" for making a root cellar like storage. Install the barrel on a slant and perhaps add a shelf so that the weight of the stored goods don't rest on the bottom layer of goods.
Savonious rotor, windmill like device to power ???????
http://www.acs.comcen.com.au/buildsav1.html
If you feel that you can get the chemical residue out, cut the barrels in half and make water tubs for smaller livestock needs.
Fire pit
Cut in half the long dimension, install grates, some sand in the bottom, and use them for large BBQs with charcoal or wood coals.
Barrel roll games for kids and adults. Add a little sand to make it more interesting.
Mount a plank to the side of a barrel laying on its side, and you have a teeter totter.
Fill with earth, sand, concrete chunks, etc. and make portable fence posts to which you fasten temporary fencing. Smaller animals only please. Large ones would probably move the fence and barrels around by leaning on the fence.
Cut in half or on a slant, add a wheelbarrow type of whell, a couple of handles, and voilà you have a cheap wheelbarrow. Well, if you have a front wheel already. Boughten ones are big bucks.
Mount on a few posts and you will have the largest mailbox on your block.
Between trees or posts, suspend from a rope going through a bung and a hole in the opposite end, add a saddle, and you have just given kids a bucking horse. YIPEE!!!!
Add legs to a barrel and you have a saddle stand.
Barrels on end with some planks across them make portable stand up eating tables.
Maybe garage sale tables. Hey, there you go--invest in some planking and rent garage sale tables. You pick up the planking at the end of the sale and let them keep the barrels to haul the unsold goods off to the dump in.
Just have a few cups of coffee and let your mind run wild. Hm, is that 2nd pot of coffee ready yet?