iPhone (Jailbroken): Whether it's the simplicity, ease, app selection, or carrier contract that keeps you on your iPhone, it doesn't mean you're not a little envious of some of the other platforms. If you're jailbroken, the amazing customisation app Dreamboard can help you make your iPhone look and feel like another OS while still retaining the things you love. All you need are these great themes.
Endroid will give your phone a fairly standard Android look, a bit similar to what you'd find with HTC Sense. Aside from just adding a new aesthetic, it also provides an animated weather widget and the ability to add web clippings to your home screen. Even the wallpaper will move behind your icons as you navigate between home screens. Want to give this theme a try? Endroid is bundled with Dreamboard, so just search for and download Dreamboard in Cydia to automatically have this theme. For an alternate option, download HTC HD2.
OS 7 will provide a Windows Phone 7-like experience on your iPhone's homescreen, complete with tile animations and all. You can easily pin apps to your start screen, just like in Windows Phone 7, and navigate through all your apps in a simple list.
To get this theme, just search for OS7 in Cydia and download it to your phone. You'll then be able to select it in the Dreamboard app.
webOS is the aptly-named webOS theme for Dreamboard, providing an interface similar to what you'd get with Palm's/HP's currently-in-limbo operating system. Most of what you'll get with this theme is visual, but if you want to add card-like multitasking you can always purchase Multifl0w for $US5.
To get the webOS theme, you'll need to buy it here for $US1, then transfer it over to your iPhone using iPhone Explorer or SSH.
For more on how Dreamboard works and how to set up your themes, read our guide to customising your iPhone.