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 HookBetter Late than Never
Some bad guys have arrived and done some bad guy things. The PCs were none the wiser. The bad guys have now made good their escape, and the PCs have caught wind of it in time to chase them down before they make it back to their lair, their home nation, behind enemy lines, etc.
PlotSeries of Villains
This is a very dramatic plot, and very well-suited to oriental campaigns. In it, the heroes have undertaken a quest, usually the finding and defeat of the Master Villain. They may have to travel to his citadel, or head off in another direction to find some artifact capable of defeating him, or run away from pursuing villains until they can figure out what's going on. All along their route, they are set upon by villains -- each villain has a name and distinct personality, and each encounter is life-or-death for the heroes and villains; the villain never escapes to safety if the tide turns against him, he fights unto death.
ClimaxPrevented Deed
Here, the heroes have been defeated -- captured by the Master Villain, or so thoroughly cut up by his minions that all believe them to be dead. And the heroes have learned, from the bragging of the villain, loose talk of his minions, or examination of clues, what is the crucial event of his master plan. In any case, the battered and bruised heroes must race to this site and have their final confrontation with the villain, bursting in on him and his minions just as the knife or final word or key is poised, and prevent the awful deed from taking place -- and, incidentally, defeat the master villain and minions who beat them previously.
General SettingUnder the Ground
In this variety of adventure, the heroes descend into vast cavern networks beneath the earth's crust. There, they can encounter bizarre races and primitive tribes, hitherto-unknown monsters and strange landscapes.
Specific Setting IMansion of a Lord
This can be the home of a villain -- the characters may have to break in and rescue someone or steal evidence, or break out if they've been captured -- or of a heroic ally, in which case it may be used as the headquarters for the heroes' plans and activities.
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 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/NeutralGibbering Madman
Some poor wretch blundered into part of the master villain's plan and saw too much. What he saw drove him crazy. He gibber and jabbers, occassionally uttering clues about what he's seen, but just isn't coherent. He knows enough that the heroes will need to take him along to comment on what they're encountering, though, so he can't just be met and forgotten.
Monster EncounterAssassin Monster
This mosnter, at some time in the adventure, is sent by the Master Villain to attack one or more heroes when they're at their most vulnerable -- asleep, enjoying themselves, etc. Usually, the Assassin Monster attacks, but the hero, though injured, is able to hold it off long enough for his friends to respond to his shouts. The Assassin Monster is usually killed by his friends, who can then speculate on who sent it and why.
Character EncounterTruthful Accuser
This encounter is like the Lying Accuser except that the accuser is telling the truth. Dig through your characters' pasts, uncover a misdeed or two, and, when the heroes are at a critical point in their adventure, confront them with someone they actually have wronged. This person has found them and appealed to sympathetic local authorities. The heroes will have to make good or have the authorities on their backs for some time to come.
DeathtrapStampede
Should the heroes ever cross plains or prairies, their villainous enemies may wish to stampede a herd of large animals at them. Alternatively, beasts in the forest may be stampeded by fires set by the villains; in this case, it will not be one sort of animal charging through, but a mixture of terrified forest animals, from the smallest fox-cub to the largest bear.
ChaseAerial
The heroes could be riding pegasi or friendly griffons or allied great eagles; the villains could be carried aloft by gargoyles or demons. The prospect of taking a mile-long fall if one's mount is hit is a very daunting and challenging one for the hero.
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 WeaknessLack of Familiarity
The Master Villain, if he comes from the past or another dimension, or belongs to an alien race, might be sufficiently unfamiliar with this world that he essentially defeats himself. How? By making incorrect guesses about human behaviour. One classic error involves underestimating the human capacity for self-sacrifice.
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 QuandryFriend Quandry
At a critical point in the story, one of the campaign's NPCs makes an impossible demand of one of the heroes.
Red HerringFalse Path to the Artifact
Once again, if the heroes have had too easy a time finding the artifact capable of destroying the villain, give them trouble this way: When they get to the place where the artifact is supposed to be contained, they find the coffer or chamber or whatever empty, obviously looted by robbers, who have scrawled such remarks as "Kelrog was here!" upon the walls.
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.