Is there a key to trigger the home button on an external iPad keyboard?
Unfortunately, the answer appears to be no. The Apple iPad Keyboard Dock for the first generation iPad had a physical home button on the keyboard, but successor products compatible with the iPad 2, including the Apple Bluetooth Keyboard have been unable to replicate this feature. Not the answer you're hoping for, I'm sure, but I'm afraid it's the answer, for now. Of course, Apple could change all this with a software update.