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.
GoalSurvive Environment
The characters could end up in a hostile environment which they must cross -- a desert, a jungle, or other hostile setting. In the course of the adventure they'll need to find food and water, resist the elements, and perhaps fight off attacks of the natives.
Story HookOld Friend
Another classic story hook is the Old Friend, the childhood friend of our hero, who shows up in one of several ways to drag the hero into the story.
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 SettingTorturous Terrain
The adventure takes place in some sort of unsettled, uncivilized, dangerous terrain; in action stories, the desert and jungle work best; choose one of those two or decide on a setting that is similarly dangerous and exotic.
Specific Setting ILost City
This is the remnant of some lost civilization or expedition, still thriving in some forgotten corner of the world. Remnants of lost civilizations can even inhabit cavern systems beneath campaign cities, preying on the above-worlders for their goods, slaves, and sacrifices.
Specific Setting IIPalace of the King
The heroes could be here for many, many different reasons: Trying to get a favor from the ruler, part of some nobleman's retinue, members of the palace guard, sneaking in to save the ruler from assassins, sneaking in to assassinate the ruler, thrown into the dungeon for crimes they did or didn't commit, etc.
Master VillainZealot
This villain is like the Conqueror, but he's not trying to conquer to own; he's trying to purge the world of something he feels is pure evil (another religion, a human, demi-human, or nonhuman race of sentient beings, a custom). He operates just like the Conqueror, enslaving or killing all those who belong to the "wrong" race or philosophy.
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 IIChief Assassin
The Chief Assassin is the favorite killer of the Master Villain. The Assassin works mostly in the field, first killing witnesses who might prove harmful to his master, then zeroing in on the player-characters. He usually meets his end before the adventure's climax, but he may taken one of the heroes down with him.
Ally/NeutralInquisitive Chronicler
This character is a historian who wishes to accompany the heroes to record their exploits. He constantly pries into the heroes' backgrounds, asking questions that are none of his business, as the adventure continues.
Monster EncounterTerrain Monster
Don't forget the simple run-in with the animal belonging to the terrain where the heroes are: Every type of wilderness has its predators and big, nasty herbivores.
Character EncounterSeducer
One of the characters is invited to a romantic liaison with an attractive local. This local can just be interested in a brief tryst, could fall madly in love with the hero and follow the hero through the rest of the adventure, could be a Loving Deceiver monster encounter, could be a thief and rob the hero blind, or could be a spy or assassin working for the Master Villain.
DeathtrapAvalanche
This is an outdoors trap. Some time when the heroes are in a narrow canyon or gorge, or are on a snow-covered mountain, their enemies can arrange to dump an avalanche upon them (rocks and boulders in the first instance, snow in the second).
ChaseWater
Don't forget the water chase: Whether it's a battle of seamanship between naval vessels, a chase of rafts toward the inevitable waterfall ahead, a contest of canoeing ability, or a chase between the villain and his giant shark vs. the heroes and their dolphin friends, the water chase can be a distinctive and dramatic one.
Omen/ProphesyBirthmark
One of the heroes has a birthmark that pertains to the adventure in some way. He may have a birthmark identical to some NPC -- for instance, some person endangered by the Master Villain. This mystery can give the hero his reason to become involved. Alternatively, his birthmark may mark him as a hero fulfilling some ancient prophecy.
Secret WeaknessLove
The Master Villain possesses the "weakness" of genuine affection or love -- probably for some NPC, though it could be very intriguing if the object of his affections is a player-character. The heroes can then defeat the villain by holding his loved one hostage, or proving that his loved one will be seriously harmed, betrayed, or killed if the villain keeps up with his activity.
Special ConditionMagic Doesn't Work Right
If the adventure is taking place on an alternate plane, then that plane's magic works oddly or not at all. (A spellcaster will find that just making himself useful is a challenge when none of his spells works.)
Moral QuandryHonor Quandry
You want to use this on the character with the most strongly developed sense of personal honor -- someone who has lived all his life by a strict code. Toward the end of the adventure, this character realizes that the best way to defeat the Master Villain is a violation of that code. For instance, the character might be a paladin, who discovers that the only possible way for the heroes to defeat the Master Villain is to sneak up on him and stab him in the back.
Red HerringLoony who Has It Wrong
You can have the heroes "aided" by a so-called expert who is actually a lunatic who doesn't know anything about what he's talking about. Once he's led the heroes off to some remote part of the continent, his evasive answers and bizarre behaviour will alert them that he really doesn't know anything about what he's pretended to be an expert on.
Cruel TrickMission is a Ruse
In the course of their adventuring, the heroes discover they have been tricked into performing a mission which helps the Master Villain.

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