These ideas do not need to be a literal bulletin board - they can be used to create rumors ("Did you hear?...") or as announcements by town criers and the like. In those worlds where the printing press is there and newspapers exist, then these could be found there as well.
Without further ado…
Edit for Edits sake!
Additional Ideas (6)
Looking to buy Exotic Monster Specimens - Live or dead! Compensation based on rarity and powers. Enquire at The Crystal Retort and ask for Het!
The alchemists at the Crystal Retort are able to make magic items from the remains of enchanted monsters. They are willing to pay good money for monsters with special powers, alive or dead.
Do you have special talents? Enjoy entertaining?
Or are you a sturdy warrior looking for employment suitable for your skills?
The Carnival of Forgotten Souls is always looking for fresh blood and sturdy guards.
Enquire in person at the Main Tent!
The Carnival of Forgotten Souls
Desperate for cash? Down on your luck?
We pay good gold for test subjects!
Enquire at the Poisoner's Guild, Street of Arcana in Talabar.
This is for real. The local Poisoner's guild (which also works on most types of potions) is looking for human guinea pigs for testing their potions. In most cases this should not be lethal, but anything short of that could be the result. One could use the Flawed Potions submission to generate the effects of test potions...
Wanted: Sturdy warriors to help retrieve a relic from heathens!
The local preisthood have learned of a new supply of Agnoscite and are looking for some muscle to help them seize it. The priesthood, of course, is not too concerned with an accurate job description.
Wanted: Exterminator, preferably one with experience with magical creatures. Apply at the Sapphire Tower.
Wizard seeking help clearing lab of magical pests Crystal Hornets.
"Why stand by while these heathens corrupt our youth? Why, they cavort with man-beasts half naked without shame! They engage in baudy humor and display proud beasts in chains!
While the PCs are in a small and unexciting village, The Carnival of Forgotten Souls arrives. An intolerant local religious leader, incensed at their licentious displays, preaches in the Village Common, stirring up trouble and urging that "those heathen scum" should be run out of town.