Samsung is a supplier for apples phone. For the 1st gen iphone, they supply the GPU chip. For the later generations, from what I can remember, its the Memory chip, GPU chip, and the screen. Although it was not clear if it was the tft or the glass or whatever part of the screen.
And it is not just samsung, Majority of iphone parts came from a taiwanese supplier. Forgot the brand
You guys can Google it to get more info. Heck! That how I found out about it too.
Samsung produces the System on a Chip (SoC) in the current iPhone 3GS, the S5PC100. The memory, GPU and CPU are all together in this SoC. Samsung also produces the screen, as it does for many phone manufacturers.
Foxconn manufactures pretty much the rest of the iPhone and internals, with a few select chips coming from other suppliers (like the WiFi chip etc).
The Hummingbird SoC in the Samsung Vibrant is probably the same one (though somewhat modified by Apple) that we'll see in the iPhone 4 (iPhone HD).
Not sure if we'll see this happen in the iPhone after that though, since Apple just bought Intrinsity, which up until now has been Samsung's "secret weapon" in designing the Hummingbird SoC. Apple will probably use Intrinisty to design its next SoC without Samsung's help, using only Samsung to manufacture and supply the chip.
The question is who Samsung is going to design a new chip now that Intrinsity has been taken away from them...