One of the PC's falls in love with a woman who happens to be a necromancer...perhaps she/he is allied with a group working against the PCs?
A caravan is traveling through the desert. The party is hired to capture a man who is in the caravan, and it must be done quietly, so that nobody else knows. They are given the man's name, and the fact that he is a mage, but no other information about him. The catch is that the caravan consists of ten wagons, with at least thirty or forty guards.
As the PCs cross a brigde/tree over a deep river they see the glimmer of gold and jewels lying at the bottom. At further inspection they notice that it is the skeleton of a man still holding on to a sack of treasure. Will the PCs try to dive to get it? What killed the man? Did he simly not let go of the bag he could not swim to the surface with? What cleansed his bones so? Are there flesh-eating beings that dwell in the deep? Can the players resist the chanse of being wealthy for once?
The PCs have travelled long and far. As nightfall approaches a mighty storm is unleashed. Luckily there is a lush wood nearby the path.
A good shelter for the rage of the unnamed weather gods it seams at first. As the PCs enter under the roof of this dense wood, they are welcomed by only a few drops wich is allowed trough the thick forest crown. A fire is offcourse required to warm the weary bones of the travellers. As one of the party is set to the task of collecting firewood the others settle down at a suitable location. But alas, they did not know the perils of this forest. But it seems clear to the rest of the party that something ill is at work as the woodcutters scream echo from afar.
There are more ways than one to encounter a dragon. With a low level group it's obviously not feasible to meet one in its lair and fight it. But standing on a bleak moorland, utterly exposed and vulnerable, it can be a chilling experience to see something flying far far overhead. Something that could just be an eagle, but you never know...