I am not aware of a website that provides a timeline for the book; it would probably be easiest to compile one yourself. Ten main events in the narrative might include:
1. Polly is transported by Uncle Andrew's magic rings into another world; Digory is sent after her into the unknown by Uncle Andrew to bring her back.
2. Digory meets Polly in the World Between Worlds. When they try to get back home, they instead end up in a land of darkness and ruin.
3. Digory and Polly find a roomful of frozen, magnificently dressed people, obviously enchanted. In the middle of the room there is a bell with a sign saying "Strike the bell and abide the danger, or wonder till it drives you mad".
4. Overwhelmed by curiosity, Digory strikes the bell. A tall, beautiful woman comes to life - it is the witch Jadis, who wants to rule the world.
5. Digory and Polly try to get back home, but to their horror, find they have brought Jadis with them.
6. Digory and Polly try to take Jadis back where she came from, but discover they have transported not only themselves and the witch, but also Uncle Andrew, a cabbie, and his horse to a wonderful new land.
7. A great lion, Aslan, appears, and Digory, Polly, and the others witness the creation of the land of Narnia. By bringing the witch to Narnia, Digory has inadvertently introduced evil into the brand new world.
8. At Aslan's instruction, Digory goes on a quest to rectify his sin. Riding the cabbie's horse, which can now fly, he journeys to find a magic apple.
9. When Digory returns with the apple, Aslan plants it, and a tree which will be the protection of Narnia springs to life.
10. Aslan tells Digory to pick an apple from the new tree. Digory and Polly return home, and the apple makes Digory's mother, who has been very ill, well again.