Where can I get a Thunderbolt hub or splitter?
I think that this question has already been asked: 

Does Thunderbolt support chaining multiple monitors to a MacBook Pro?

To sum it up, it is too early for a splitter or hub for a Thunderbolt port. But you can daisy chain.

And this sums it up as well: http://www.the-cable-store.com/contents/en-us/d44_lightpeak_hubs.html