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.
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 HookOld Enemy
This is a straightforward story hook; the hero learns that his oldest enemy is back and is very active in the campaign, up to something. The hero will naturally want to investigate and will walk right into the story.
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 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 ICatacombs
These can be catacombs beneath a living city or a ruined one; they can be long-forgotten or still in use.
Specific Setting IIMadman's Fortress
This is the citadel of a major enemy: Strong, unassailable, filled with soldiers and monsters, lined with secret passages and deathtraps; not a wholesome place for adventurers to spend their time.
Master VillainGod of Chance
Here you have two options. This Master Villain could be a real entity -- an actual god of mischief or silliness, who has intruded in the heroes' lives to cause chaos and have fun. Alternatively, this "villain" could actually be pure chance: The heroes are having a series of unrelated, accidental encounters which cause them fits. No real single villain is involved, although initially it looks as though there is.
Minor Villain IAvenger
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.
Minor Villain IISingle-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.
Ally/NeutralIngenue in Distress
The heroes must protect some defenseless young innocent who is in danger from the villains. This person, perhaps the sheltered son or daughter of a nobleman or merchant, has no abilities at all but is sweet, charming, and in great need of help.
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 EncounterBelligerent Soldier
The billigerent one has just had his ears pinned back by his commanding officer and is anxious to take it out on some hapless civilian. If this is a city gate, he claims that the hero's papers are wrong or that he recognizes the hero from descriptions of a wanted criminal; if this is the streets, he insults the hero's lack of military bearing, pretty looks, clothes, smell, companion, or whatever it takes to provoke a reaction.
DeathtrapTomb Deathtraps
Another classic type of trap is the sort of triggered trap left behind in abandoned tombs, ruins, and catacombs. Here, a hero who touches the wrong step, floor tile, wall brick, torch bracket, mounted gemstone, or other device will trigger some sort of ancient trap designed to kill tomb-robbers and intruders.
ChaseWater
Don't forget the water chase: Whether it's a battle of seamanship between naval vessels, a chase of rafts toward the inevitable waterfall ahead, a contest of canoeing ability, or a chase between the villain and his giant shark vs. the heroes and their dolphin friends, the water chase can be a distinctive and dramatic one.
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 WeaknessHoly Symbol
The villain may have the traditional weakness to a specific holy symbol -- but don't choose just an ordinary one. It may be a holly symbol no longer used by the church, or may be some forgotten variation of the current symbol. (For instance, the cross may not work, but a variation -- such as the Roman cross -- might; alternatively, it might have to be a holy symbol which has undergone some unfamiliar ritual.)
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 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.