In the spirit of Christmas, here are a few ideas for situations to inflict on your players:
A tribe of goblins (in or around your local dungeon) has a peculiar ritual: they sneak into adventurers' camps and leave 'gifts': pieces of rotting meat, skulls, filthy rags, and so on. This is a nuisance at least, but can quickly escalate if the goblins leave something foul in the bag with all the rations in it. Alternatively, they've been doing this to the folk of a local village, who want it to stop.
Turns out they're led by an obese, cowardly ogre who got it into his head that giving tribute can convince others to leave him alone, after one meeting with a bunch of delvers who promised not to kill him if he gave away some of his shinies.
In the village of Edgesburg, the peasants have long had a tradition of leaving an offering on their doorsteps on the night of the winter solstice, consisting of a few drops of blood on the lintel from every member of the family. Over the past couple years, the new priest of the Church just founded here (to bring light to the poor pagans) has convinced them to stop this practice as both dangerous and sacreligious. Unfortunately, after this solstice passed (the night before the PCs got there, naturally), every house in the village woke to find their youngest children hung by the rafters, bloated and leaking a bituminous substance, except those few who had secretly kept up the practice.
Perhaps it has something to do with the crypt of Peter the Terrible, rumoured to be somewhere in the forest on the southern edge of the village.
Mother of God
The party's cleric or holy warrior gets a vision: his god's next avatar is to be born soon, but the mother has been abducted by an evil cult of an opposed deity, who plan to offer mother and child as blood sacrifices to their dark goddess. They've repaired to an old warren of crypts for their ritual, which will be completed when the child is born, a month from today. Can the heroes save the child and his mother before they enact their foul plan? For those delvers of a more mercenary mind, there's sure to be treasure to be gained from despoiling the hidden sanctuary, and no doubt the god will be grateful to those who rendered him aid.
As a change of pace from digging in old ruins, a caravan has offered to hire on the PCs as guards and guides, so that they can deliver gifts from the local town to the King for his son's birthday. Of course this is in the desert. Can the PCs survive the trek across the Burning Wastes, rumoured hunting grounds of the Great Worm? What about after the unnaturally-strong sandstorm scatters the caravan, kills all the animals and other guards, and causes the gift cargo (rare spices that must be kept cool) to go missing?
For ideas around desert encounters and wildlife, I highly recommend GURPS Dungeon Fantasy Adventure 1 - Mirror of the Fire Demon. (It's also good in its own right.)