Oh, I watched Howl's Moving Castle the other night, and rather liked it. I preferred Spirited Away as more seemed to happen, but the story and animation in Howl's were both exceptional. Not read her stuff, but will get round to it at some point.

The Narnia series is also a good take on alternative universes, what with magic rings, wardrobes and paintings all providing doorways into Aslan's realm.

JB

<Added>

I always thought Clive Barker's Weaveworld had a clever take on the alternative universe. This whole world is weaved into a carpet, and rather than the characters being sucked into the carpet, the carpet unravels wherever it happens to be, overlaying part of Liverpool, and later, a Scottish valley. Read it if you haven't already.

JB