Random Adventure Generator

ThemeAction/Adventure
This is the most common and straightforward sort of adventure there is. In the Action/Adventure scenario, you present your characters with a task and then confront them with obstacles to overcome in order to accomplish the task successfully.
GoalWin War
In this adventure or set of adventures, the characters become part of an army -- a force assaulting another kingdom, perhaps, or an army defending one realm from another.
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.
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 ICraftsman'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.
Specific Setting IITemple/Church
This can be either the church of some lofty and good diety, or the dark and grisly temple of some horrid deity (doubtless filled with evil soldiers and monsters), or even the temple that the madman villain has dedicated to himself for when he becomes a god.
Master VillainCorruptor
The Corruptor is the villain who wants to make something nasty out of something that is currently nice. He may be working on a small scale -- i.e., wish to corrupt one character or a few characters, particularly PCs and their favorite NPCs. Alternatively, he may be a big-scale villain trying to change an entire city or nation into a jaded, debased pit of sin, hatred and death.
Minor Villain ISingle-Minded Soldier
This most trustworthy of villain minions is the experienced, competent, persistent soldier -- a field-trained officer who serves the villain with military precision. He is usually encountered in the field as leader of the villain's field operations. He is not encountered directly until the middle of or the latter part of the adventure; until then, the heroes encounter only his subordinates.
Minor Villain IIAvenger
This character is much like the Master Villain of the same name, but he's not in charge of all this villainy, and he's definitely an enemy of one of the player-characters. You'll have to decide who he is and why he hates one of the heroes; he could be anything from a recurring villain to someone who simply lost a fight to the hero once.
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 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 EncounterNew Enemy
In the course of his ordinary activies, one of the heroes can make a New Enemy. Hurrying along the street, he can bump into a disagreeable fighter for whom an apology isn't enough; in a tavern, he can make some innocuous remark that you deliberately have the irritable fellow misconstrue as an insult. The New Enemy will only exchange heated words with the hero at this point, but will appear again later in the adventure and will eventually have to fight the hero.
DeathtrapMutually Assured Destruction
In this very nasty deathtrap, the heroes are bound up in such a manner that any one of them may get free of his bonds -- but when he does, all his friends perish. Obviously, the heroes' task is to find some way for everyone to get out alive. Perhaps an intricate series of cooperative rope-cutting will defuse the trap; perhaps a coordinated maneuver will get everyone free as the trap is being sprung.
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/ProphesyTotem Animal
If a hero has an animal which is his totem, he may see the animal engaged in a fight to the death with another animal -- one which, coincidentally, is the totem of one of the villains. How his totem defeats the other -- or is defeated by it -- gives the hero some clues as how to fight his actual opponent when the time comes.
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 ConditionNo Lawbreaking
For some reason, at one point in the story, the heroes cannot allow themselves to break the law -- even when it would help them greatly to do so. For instance, the heroes may be asking for the help of a king whose word is law and whose power is immense. When they arrive for their audience, an emissary of the Master Villain is making a similar plea for help. If the heroes attack and kill that emissary, they will lose any chance at the king's help -- in fact, he may order their execution.
Moral QuandryRespect Quandry
This is much like the Ally Quandry, only at a greater distance. The heroes have been utilizing the aid of two (or more) powerful NPC allies. Now, in the course of the adventure, the heroes come across a task which can be accomplished in one of two ways -- say, through military intervention or by esoteric magic. The problem is, the NPC allies are arguing for different choices, and the one whom the heores choose against will no longer aid them.
Red HerringArtifact that Doesn't Work
Often, epic quests against powerful Master Villains require that the heroes find some legendary artifact, the only object which can defeat the villain. If your heroes have had no trouble getting to the artifact -- they've effortlessly sliced through every obstacle you've put in their path and are confidently advancing on the resting place of the magical item -- you can have it not work.
Cruel TrickWanted by the Law
One final complication, one which occurs pretty frequently, is when the heroes are wanted by the law. When they're wanted by the law, they have to travel in secret and very limited in the resources they can acquire.

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