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 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.
PlotGeographic Progression
This is the simplest sort of adventure plot. The heroes have an area to investigate or travel through; they have encounters based on where they are. For instance, the traditional dungeon, where monsters are tied to specific rooms or areas. Or, if the heroes are travelling along a narrow valley or through an enchanted forest, they might suffer ambushes and other encounters fixed to various points along their travel plan. The plot, then, is getting to the villain by surviving the intervening obstacle encounters.
ClimaxChase to Ground
First, you have the Heroes Chasing the Villain. The villain, after a series of encounters with the heroes, is running to safety, to some place where he can acquire more power, or to somehwere he can accomplish some dread purpose such as assassination or mass murder. The heroes chase him, have to deal with the obstacles he leaves behind, and finally catch up to him before or just as he reaches his goal. Here, we have the final duel between the villains forces and the heroes. Second, you have the Villain Chasing the Heroes. Often, in a story like this, the heroes have found out how to defeat the villain -- such as getting to a particular temple and conducting a particular ritual. The villain chases them all through their quest, catching up to them just as they're commenciing their ritual; they must, with heroic effort, conclude the ritual while suffering his attacks. Third, you have the Master Villain's Sudden Escape Attempt. This takes place in adventures where the Master Villain's identity is unknown until the end. His identity is revealed and he makes a sudden bolt for freedom; the heroes give chase. This usually results in a dangerous foot-chase through nasty terrain -- such as across rooftops, through the dungeons, or across an active battlefield.
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 ICatacombs
These can be catacombs beneath a living city or a ruined one; they can be long-forgotten or still in use.
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 VillainRavager
This Master Villain is like the Destroyer, except that he terrorizes a very limited area -- such as a village, island, castle, or clan stronghold. (He may want to destroy the whole world but be trapped where he is; perhaps his efforts to free himself constitute the adventure's plot.) He stays in his area and terrorizes whatever comes into it.
Minor Villain IChief 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.
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/NeutralTalkative Barkeep
This classic encounter is the garrulous innkeeper who has information the characters want; trouble is, they'll have to bribe him to get it, or agree to stay at his inn, or buy a lavish meal, or listen to his incessant stories about his career in the army, or whatever.
Monster EncounterRavager
This is another classic monster encounter; the monster which is bedeviling a community or local area and will continue to do so unless the heroes destroy or defeat it. Yes, this is similar to the Master Villain of the same name, but the Ravager usually has no master plan -- it just wants to kill, destroy, or eat.
Character EncounterOld Friend at the Wrong Time
When the heroes are trying to sneak through a guardpost, citadel, or city where they can't afford to be recognized, one of the characters' old friends recognizes him and loudly renews their acquaintance in full view of the guards looking for the characters. This usually leads to an exciting chase as the heroes must escape.
DeathtrapPit and the Pendulum
Actually, we're applying this term to any of many time-delay deathtraps. In this sort of trap, the villains capture the heroes and place them in a trap which will soon kill them -- it operates on a delay, often based on a timing device or a burning fuse.
ChaseEndurance
The Endurance Chase is not some sort of climactic chase -- it's a rugged, tiring, persistent pursuit that tests the characters to their limits. In this chase, the heroes and villains are pursuing one another across a lot of territory and they're not catching up with one another very fast. This may be a horseback pursuit across a hundred miles of savannah, a camel chase across several days' worth of desert, or a chase across arctic tundra.
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 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 QuandryAlly Quandry
You set up the situation so that the heroes have a good chance at defeating the Master Villain if they get the aid of two specific individuals, probably experts in fields relating to the villains' activities. But the two experts hate one another and refuse to work together, even if it costs them their world.
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 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.