Some ideas for different types of creatures with extracts:
Wax Beetles: They make termite-like hives out of wax. The wax could be made similar to beeswax, and perhaps it could harden to be useful in crafting.
Glue Slugs: Live in small bubble-like sacs, and produce a goo that when mixed with something (water, ash, dirt, whatever), makes a strong-bonding agent.
Ash Salamanders: Make a nest of foraged wood/bark, and produce enough heat to turn it to ash/charcoal.
A use for pixies: Maybe if they were treated properly, like given a small room for a home, and fed/watered/entertained, they could turn small amounts of regular rock and metal into precious rock/metal/gems?
Pitcher Plants: when fed with almost any kind of plant/animal matter, produce nectar/honey. Maybe a dwarven-bred strain produce alochol.
Some Ideas for insects in Haunted/Terrifying Areas:
Molten Ants: 3 inch Ants, their bites and stings inject lava into their victims. Trained: Maybe, in large enough amounts, could produce lava?
Rime Locusts: Their flapping wings spread devilish frost over everything they swarm over. They consume their prey once it's flesh is frozen solid. Trained: Could freeze water, perserve food?
Acidpedes: Centipedes with a caustic sting, they quickly dissolve anything foolish enough to stand in their way. Trained: Could mine without leaving stone behind, maybe their acid doesn't affect gems or metal?
I imagine all these things could be trained with an animal trainer, or maybe an "Insect trainer". The Pitcher Plants could be farmed like other plants.