A full list on how to get double (or more) drops from various things, sorted by type... Remember all the boosts can be maximised by using ready boosts while they last.
Animals
Shearing For Shave Tails
Comes from: Crafted in the Library
Duration: 15 Minutes
How to use: Activate the boost and click animals.
Note: This can be used with any Feeder tool and does work on stored animals. This also works on healable items that are classed as animals.
Crops
Crop Whisperer
Comes From: Crafted in the Library
Duration: 15 Minutes
How to use: Activate the Boost and harvest Crops.
Note: This works while using the Harvester, inside the Greenhouse and on crops harvested inside the Raised Beds.
Crop Mumbler
Comes From: Mission Rewards
Duration: 5 Minutes
How to use: Activate the Boost and harvest Crops.
Note: This works while using the Harvester, inside the Greenhouse and on crops harvested inside the Raised Beds.
Spouse Memory Boost
Comes From: The Daily Bonus of the Memory Cabinet.
Duration: 20 Minutes
How to use: Activate the Boost, SELECT YOUR SPOUSE and harvest Crops.
Note: This only works on crops harvested by a SPOUSE avatar. It does not work with the Harvester, inside the Greenhouse or in Raised Beds.
Lumber Trees
How to Jack Lumber
Comes From: Crafted in the Library
Duration: 15 Minutes
How to use: Activate the Boost and chop trees.
Note: This works while using Baby Bunyan, Sharp Axe, Golden Axe or a Chocolate Rush. It also works on chops from the Lumber Yard.
Fruit Trees
Spouse Memory Boost
Comes From: The Daily Bonus of the Memory Cabinet.
Duration: 20 Minutes
How to use: Activate the Boost, SELECT YOUR SPOUSE and harvest Trees.
Note: This only works on Trees harvested by a SPOUSE avatar. It does not work in the Orchard or with the Tree Harvester.
Peppermint Earthquake
Comes From: Crafted in the Candy Shop
Duration: 15 Minutes
How to use: Activate the Boost and harvest Fruit Trees.
Note: Unlike other boosts this TREBLES drops. It works on Fruit Trees tended inside the Orchard and while using the Tree Harvester.
Debris
Squeezing the Stone
Comes From: Crafted in the Library/Mining Collection
Duration: 15 Minutes
How to use: Activate the Boost and clear debris.
Note: This works while using the Debris Clearer.
Buildings
Daily Doubler
Comes From: The Town Hall Menu or the Town Hall entry inside the Civic Centre
Duration : 2 Minutes
How to use: Activate the boost then collect building bonuses.
Note: The Boost can be reset by crafting a Doubler Reset inside the Town Hall. You can only hold TWO Doubler Resets in your inventory at any time.
Decorations
Espresso Boost
Comes From: Mission rewards and bought in the Gold Dust Market
Duration : 15 Minutes
How to use: Activate the Boost and Collect the Daily Bonus from Decorations.