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.
GoalSettle a Debt
A player character may find himself in the position of needing to settle a debt. He could gamble away all his money and need to raise some more to repay the gambling house before its enforcers come for him. On a more personal level, the character may need to settle a debt of either money or honor that he owes to an NPC.
Story HookMistaken Identity
The hero could be mistaken by one villain for another villain involved in the master plot. This has good comic potential if the hero and missing villain are in fact so similar that no one can tell them apart. (This is even more fun if they turn out to be long-lost twins.)
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.
ClimaxThrone Room Duel
This is set up much like the Scattered Duels, except that you don't separate the heroes. It's harder to control whom fights who in this situation... but if it doesn't matter who has the final duel with the Master Villain, this is a classic climax choice.
General SettingOn the Sea
Most of the action occurs on the sea -- the heroes are shipborne for some reason, docking in lots of ports. Again, this is good for adventures where the heroes are investigating clues left all over the map, are part of some trading enterprise, or are being pursued by villains.
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 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 VillainAgent Provocateur
This Master Villain is a clever spy who inflitrates an organization, order, or army, and tries to effect its destruction by getting it to perform actions which will cause others to oppose it directly. The identity of this Master Villain is usually a closely-guarded secret; the heroes will encounter his cover identity, but will not suspect that he's responsible for all this chaos until they start adding up clues. Females in this role can be very, very effective.
Minor Villain ISnivelling Vizier
The Vizier is a throne-room villain. Functionally, he's rather like the Hard-Eyed Advisor, offering tactics and advice to his master; but he's an ooily, sleazy, cowardly sycophant. He's usually brilliant in his field of advice but has no combat abilities.
Minor Villain IIMoronic Muscleman
This fellow is a huge, powerful monster of a fighter. His job is to smash anything the villain tells him to smash. He does that very well, but don't ask him to do any thinking; he has no time for such brainy stuff.
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 EncounterInquisitive Official
Some local authority has noticed the characters' presence and it makes her curious. She snoops around asking questions all the time. She may be a city guardsman or special agent of the ruler, but (functionally) she's a police lieutenant, asking the rong questions at the wrong time; the heroes have to work around her, sneaking where normally they'd be able to work in the open.
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.
ChaseHorseback
This is a relatively short chase -- it only needs to go on for a mile or so before even the best horses are winded. If it goes on longer than that, the horses may collapse and perhaps die.
Omen/ProphesyInnocent Fulfills Prophecy
An innocent could fulfill a prophecy -- one which endangers his/her life. This innocent might, for instance, be the one who is supposed to slay the king, but is not a mighty adventurer able to protect himself from the king; the heroes may find themselves sheltering and helping this poor dupe.
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 Weapons Allowed
At some point in the story, the heroes must surrender their weapons. Perhaps they're visiting some quarter of the city where weapons are not allowed; or a particularly peace-loving temple. In any case, once they're there, they are attacked by enemies belonging to the Master Villain.
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 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 TrickNPC Turns Traitor
He may alert he enemy when the heroes are planning a raid; he may steal the artifact and take it to the villain; he may stab a hero or important NPC in the back (literally) before departing.

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