harry potter - How many ways are there of getting to Hogwarts?

In the books, we see the following:

Train

This is the obvious one, since Harry takes the Hogwarts Express for five of the six years he attended Hogwarts.

Flying car

As seen in Chamber of Secrets, Harry and Ron used the Weasleys' flying car.

Knight Bus

In Order of the Phoenix, Harry, Hermione and the Weasleys take the Knight Bus from Grimmauld Place back to Hogwarts after the Christmas holidays. Technically this took them to Hogsmeade, but I'd say that's close enough to count since that's where the Hogwarts Express stops too.

Portkey

In Order of the Phoenix, a Portkey is used to transport Harry and the Weasleys from Dumbledore's Office to Grimmauld Place, and another one is used to transport Harry from the Ministry of Magic back to Hogwarts after Dumbledore's duel with Voldemort.

Floo powder

In Order of the Phoenix it's shown that Hogwarts is connected to the Floo network, though I'm not sure anybody actually uses that to travel to or from Hogwarts.

Apparition

Harry and Dumbledore Disapparate from Hogsmeade (see the Knight Bus entry on "close enough") to the Cave containing the locket Horcrux, and back again.

Flying (Broomstick and Thestral)

Harry and co use a combination of broomstick and Thestral to fly from Hogwarts to the Ministry of Magic; there's no reason they couldn't have used the Hogwarts Thestrals to find their way back again if necessary. Dumbledore travels halfway to the Ministry of Magic from Hogwarts (presumably by Thestral) in Philosopher's Stone, then returns to Hogwarts (presumably the same way).