The Automatic waterer that I use to supply water to my chickens.  If you wouldn't drink the water then your chickens should not have to drink it.

Supplying water to chickens in an open bowl invites contamination with faeces and dirt.

Ground eggshells.  I make this by first squashing my saved eggshells then running them through a vitamiser.  However I rarely feed it to my chickens, preferring to spread it around young seedlings as a deterrence to snails and slugs. 

Ercildoune sand.  It is in fact a fine gravel which comes from a quarry in the Ballarat area.  As well as to provide grit for my chickens I use it to make potting mix and  on the vegetable beds.