Using the Apple Wireless Keyboard with an iPad with PC/Mac-like keyboard commands
BeeKeyboard is a tweak available via Cydia that adds the ability to create custom keyboard shortcuts. I'm not sure if it can do app-switching shortcuts, but you can install a plugin called BeeSafari to add some browser shortcuts.
When you’re in a programme, press and hold the CMD button, a pop-up should appear giving you a list of commands.