FYI, check out Shadow of the Beast and its sequels for some of the sweetest parallax scrolling encountered on the Amiga...
I've always wondered how they managed to create more than two "playfields" of scrolling... I've even messed with asm, and still I couldn't fix me something up that would give the impression of several layers fast enough..
Thinking again: anyone knows of technical docs floating around (on game development, gfx tricks etc.) specifically for the Amiga? (Not the ROM kernels please, I copied those books by hand a long time ago. With "by hand" I mean pressing the buttons of a coying machine