Android (rooted and unrooted): If you've ever wished you could use a keyboard in landscape mode that is different to the one you use in portrait mode, Keyboard Manager will do just that. The app lets you switch between them whenever your screen orientation changes.
You just need to pick which keyboard you want to use in landscape mode and which keyboard you want to use in portrait mode. You can also set the keyboard based on individual apps.
We've mentioned Keyboard Manager once before, back in its early days, but Lifehacker reader huh989 discovered that the developers released a new version, called Keyboard Manager Plus, that doesn't require root. You'll have to deal with a quickly disappearing popup once in a while (and a $1.99 price tag), but it's a great option if you don't want to root your phone.