JH NameGen Gold has an Adventure Hook generation ruleset that comes with it. It can give you ideas ranging from funny to thought-provoking to just plain crazy. Here's some samples:
A respected craftsman has asked you to negotiate with some orcs who are invading the countryside.
You were framed for robbing a local celebrity.
In return for freedom, a former adventurer's evil twin brother told you where to find bandits who are blackmailing government officials.
A family friend is missing. And so is a popular local man's signet ring.
After raiding the hideout of a group of goblins, you discover a book of accounts that you think belongs to a local cleric.
A map of a long-forgotten underground lair was found, and it appears that there's treasure hidden inside.
The town's sheep are missing.
A well-known noble fled mysteriously during the night, leaving only this note.
Your former mentor was seen entering a catacomb under the cemetery, and has not yet returned.
You overhear evil mercenaries plotting to ambush nearby tribesmen.