Random Adventure Generator

ThemeHorror
This type of adventure is designed to scare both the characters and the players. Just having a monster attack is not enough for a horror theme; the monster must first frighten the characters.
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 HookPressing Buttons
As a general story-hook approach, think about the player-character -- his personal goals and his personal dislikes. If the hero is pursuing a specific goal, you have one of the minor villains, as a side-effect of the villain's master plan, thwart the hero's latest step towards that goal. Alternatively, if there's something the hero truly hates to see, have it happen -- and have the villains be responsible.
PlotAccumulation of Elements
In this sort of plot, the heroes have to go from place to place -- perhaps covering very little area like a city, perhaps roaming the known world -- and accumulate elements to be used against the Master Villain. These elements may be clues, pieces of an artifact, evidence, or allies.
ClimaxBloody Battle
This is the best Climax for an adventure involving the clash of mighty armies -- or for any adventure where, toward the end, the Master Villain and a large body of minions confront the heroes and their own troops. This finale is characterized by a monstrous clash between the two forces, with the heroes chewing through the enemy ranks to get at the Master Villain and his elite guards. It's strenuous, exciting, and classically simple.
General SettingExotic Distant Land
The adventure will take the heroes to some fascinating and exotic distant country, where they'll have to cope with new customs, monsters unfamiliar to them, and very colorful NPC encounters; choose one of the more fascinating foreign lands from your campaign world.
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 IICraftsman's Quarter
This can occur in either the shop of the master craftsman of a palace or manor, or the guild-area of a city.
Master VillainSufferer
This Master Villain disguises himself as some other sort of villain. Long ago, he was given an ugly curse -- he longs for death but can never die unless slain by heroes unaware of his curse. (Naturally, the way the curse works, he has to defend himself when attacked by the heroes.) So this villain works hard to make sure the best heroes in the world have sufficient cause to want to come and kill him. He'll insult them, ruin them, kidnap or murder their loved ones, whatever it takes to bring them against him. Often, he can only die -- his curse can only be undone -- in one specific holy place, so he'll have to lure the heroes to that place to face him. If the heroes are doing research on the villain all this time, they may find out his secret, leading to a sad and painful end to the episode as the unkillable villain has to leave and find someone new to kill him.
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 IIHard-Eyed Advisor
This is the sort of villain whom the heroes see in the Master Villain's throne room. He's hard-eyed and scary; life means nothing to him and he enjoys killing. He's also a good advisor to his master.
Ally/NeutralAbsent-Minded Expert
The characters find they need an expert in some fields -- pottery, alchemy, whatever -- but all they can find is a somewhat daffy and absent-minded master of that subject. He's useful when around his subject matter, but otherwise absent-minded, incautions, in frequent need of rescuing, etc.
Monster EncounterNoble Beast
With this encounter, the heroes find that they have to capture -- but not injure -- some sort of powerful, noble beast in order to accomplish their mission. For instance, to reach a mountain-top aerie, they must capture pegasi and ride them up to their enemy.
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.
DeathtrapDemolition Zone
In this classic deathtrap, the heroes are placed (usually bound and weaponless) in some building or area just as it's due to be destroyed.
ChaseSpecial Terrain
You can make any chase more memorable by having it take place in a setting to which it is utterly unsuited. For instance, horse chases are fine and dramatic when they take place through the forest, out in the open plains, or along a road -- but they become diabolical when they take place inside the Royal Palace or in dangerous, labrynthine, treacherous catacombs.
Omen/ProphesyHero Fulfills Prophecy
This is the most useful sort of prophecy. In the early part of the adventure, one of the heroes discovers that he fulfills some ancient prophecy.
Secret WeaknessElement
The Master Villain can be banished, dispelled, killed, or otherwise defeated by some of element or item. The Master Villain tries to get rid of all the examples of this element in his vicinity; he doesn't let his minions carry it or bring it into his presence. But he's not stupid; he doesn't announce to the world what his weakness is. He tries to hide his concern within another command. If he's allergic to red roses, for instance, he orders all "things of beauty" destroyed within miles of his abode.
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 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 TrickVillain Accompanies Party
In this distressing situation, the Master Villain, in disguise or his secret identity, accompanies the heroes for much of their quest. He gets to know them, learns their strengths and weaknesses, learns their plans, and just as soon as it's most efficient for him, he thwarts their current plans and leaves. Alternatively, the Master Villain might be with the heroes all along, up to the very end; the heroes know that one of their companions is the villain, and the whole thrust of the story is finding out who he is. This is the whole purpose of most Mystery-type adventures.

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