Well, what with a war or god trying to enter the world in every book, there are a number of big events. In fact, almost every book or trilogy is about a big event, so events are listed by book.
i=incomplete
Chronicles
The War of the Lance
The Chaos War i
Legends
Raistlin's attempt to become a god
Fistandantilus's attempt
The Dwarfgate War
Heroes
The Great Dragon War i
Preludes
Takhisis attempt to take over the world
Brothers Majere thingy
Elves freed of Li El
Meetings
Sargonnas attempt to take over the world
Elven Nations
The Kinslayer Wars
The creation of the Qualinesti