Random Adventure Generator

ThemeRomance
This sort of adventure (rarely played, but worthwhile anyway) has as its central plot the romance between two characters, usually a player-character and an NPC.
GoalThwart Monstrous Plan
This is a classic fantasy-adventure plot: The characters learn of some horrible plan made by a monstrous enemy, and must thwart it before the kingdom is lost or the world is destroyed. This is an epic goal, and usually requires that the characters go to all sorts of places, rounding up allies and artifacts, before being strong enough to face their enemy.
Story HookMissing Memories
One or more of the PCs wakes up with no memory of the recent past, and now they find themselves in some kind of trouble they don't understand. The PCs must find the reason for the memory lapse, and solve any problems they uncover in the meantime.
PlotEvent
For this plot, choose some sort of event -- a tournament, a holiday, a celebration called by the king, a masked ball, or whatever -- and set the commencement of the Master Villain's plan against that backdrop.
ClimaxDivine Retribution
Here, the heroes' goal has been to alert the gods that the Master Villain threatens them or their plans; in the last scenes of the adventure, as our heroes face an overwhelming enemy force, the gods bring down their divine retribution on the villain, causing a massive earthquake, tidal wave, lightning storm, or flood of monsters. This is all well and good, but the heroes are too close and must escape the fringe effects of this awesome disaster. A variant on this is the Natural Disaster. No gods are actually involved, but the Master Villain has been tampering with the delicate forces of nature. He may, for instance, have been powering his master spell with the energies of a volcano. When the heroes attack the scene of his spellcasting, the spell goes out of control and so does the volcano. The villain is consumed in the eruption and the heroes must escape or be consumed themselves.
General SettingOn the Road
Most of the adventure takes place on the road, as the heroes are travelling from place to place. This is especially good for adventures where heroes are investigating a wide-ranging mystery, are part of a caravan, or are being pursued by loathesome villains.
Specific Setting IMilitary Encampment
This is best used in an episode involving warfare; it could be the good-guy army's encampment, from which the heroes launch their adventures, or the villains' encampment, in which case the heroes might have to sneak in on a mission or escape from it if they're captured.
Specific Setting IIShacktown of the Oppressed
Part of the action centers around the tenements or shacks of the worst part of town; perhaps an allied NPC lives here or the characters are fugitives hiding out in the nasty part of town.
Master VillainLovable Rogue
This Master Villain isn't really evil -- he's just chaotic and fun. Cheerful bandits in the forest who rob from the rich and give to the poor, singing and rope-swinging pirate kings, and romantic, sophisticated duellists all belong to the category of the Lovable Rogue. Often, the Rogue will not be behind the nastiness the heroes are encountering; he may be in competition with them for the prize they're seeking. Often the heroes and the Rogue (and his minions) will have to team up to succeed at their task. Just as often, the Rogue will try to get away with the whole treasure.
Minor Villain IInquisitor
This villain is the one who interrogates the heroes and NPCs captured by the villains. He accompanies the other Minor Villain out into the field and works on anyone captured; he enjoys inflicting pain and suffering.
Minor Villain IILovable Rogue
This character is like the Master Villain of the same name, except that he has no minions of his own and serves at someone else's bidding. However, he's very independent, not always working in his employer's best interests; he often makes fun of the Master Villain's pretensions and may suffer that villain's retaliation because of it.
Ally/NeutralGrumpy Old Professional
Again, the heroes need an expert in a certain field -- this time a craft or art, such as blacksmithing, engineering, horse-training, or whatever. The only or best professional they can find is an aged expert. He's grumpy, cranky, and sharp-tongued; he constantly complains about the food, the weather, his companions, the decline in skill of his co-workers since he was a young man, the road conditions, the rotten pay he's receiving, and so on.
Monster EncounterForeshadowing Monster
With this monster encounter, combat may not be necessary. This monster encounter exists to alert the characters to the fact that something unusual is going on, a foreshadowing of their upcoming conflicts with the Master Villain.
Character EncounterBandit Gang
When the heroes are en route from one place to another, have them run across one of the local bandit gangs. The bandits are faster and far more numerous than the heroes. But the bandits stay back. Basically, they're bandits who admire courage and prowess, and the bandit leader will challenge one or all of the heroes to a test of bravery or ability -- such as a horserace, a duel, a wrestling match, a joust, an arm-wrestling match where scorpions sting the loser, etc.
DeathtrapRock and a Hard Place
This trap starts out as an Animal Pit, Pit and the Pendulum, or Tomb Deathtrap, but an obvious escape suggests itself very early on. Trouble is, it leads into even worse danger. The hole out of the animal pit may lead to the lair of an even worse animal; it may lead through a succession of dangers (collapsing old catacombs, into an underground river, into a den of zombies) before the heroes reach the light.
ChaseHorseback
This is a relatively short chase -- it only needs to go on for a mile or so before even the best horses are winded. If it goes on longer than that, the horses may collapse and perhaps die.
Omen/ProphesyFortune Teller Predicts Doom
This is an ominous encounter: A fortune-teller predicts doom for one of the heroes, or for some community menaced by the Master Villain. Shortly after, some calamity should befall the hero: He can be attacked by an assassin, be in a building when it is struck by fire or an earthquake, or suffer other danger. Investigation of the events can then point the heroes toward the Master Villain as the event's instigator.
Secret WeaknessSecret Embarrassment
Finally, the villain may have some aberration or secret shame that will force him to flee when he is confronted with it. It could be something as simple as the fact that his nose is too big, or that he is a small and nebbishly wizard pretending to be some vast, powerful demonic power. When his shame is revealed, he is too humiliated to continue; this is a good option for comedy adventures.
Special ConditionTime Limit
Finally, the most obvious condition to place on an adventure is to give it a time limit. If the Master Villain is going to conclude his evil spell in only three days, and his citadel is three hard days' riding away, then the heroes are going to be on the go all throughout the adventure -- with little time to rest, plan, gather allies, or anything except get to where they're going.
Moral QuandrySaving Quandry
Finally, another classic quandry puts the heroes in the position of choosing between a grand opportunity to hurt the Master Villain -- or saving the lives of a number of individuals.
Red HerringLying Rumor
This is the worst and most useful type of red herring -- the interesting rumor which just happens to be false. In adventures of this sort, the best Lying Rumor concerns the Master Villain; it gives the heroes some "important" information about him which later turns out to be useless.
Cruel TrickNPC Turns Traitor
He may alert he enemy when the heroes are planning a raid; he may steal the artifact and take it to the villain; he may stab a hero or important NPC in the back (literally) before departing.

Based upon tables from the Dungeon Master's Design Kit by TSR, Inc.