Android: If you find yourself preferring a different keyboard in portrait mode than in landscape, free app Keyboard Manager will automatically switch between them on a rooted Android phone.
Keyboard Manager is root-only at the moment, and the install process isn't quite as straightforward as a regular package, but it's pretty handy (and not too difficult). You'll need an app like Root Explorer to pull it off, but as long as you do, it's just a matter of moving the .apk file to /system/app and changing the permissions. Once you reboot, it should show right up in your app drawer.
The app itself is pretty self-explanatory: just pick which keyboard you want in each screen orientation, and it will switch them for you automatically. It's still in development, and is not without its quirks—unfortunately, you have to orient the phone before you bring up the keyboard (it won't switch from one to the other instantly)—but it's still a godsend for those that prefer, say, previously mentioned Swype in portrait mode but want a more conventional keyboard in landscape mode. Hit the link for installation instructions and to download the app (you'll need an account at the XDA-Developers forums to do so).
Keyboard Manager is a free download for Android devices.
Keyboard Manager - Dual Keyboard: Portrait/Landscape Switch [XDA-Developers via Talk Android]