webOS's Synergy feature, which stitches together data from disparate sources into your address book (and really, throughout the entire operating system) is an idea that I wish Apple would appropriate. Apple made a big deal at this month's Worldwide Developers Conference about Twitter being integrated into iOS 5, but just about every service you can think of--AIM, Skype, Google Calendar, MobileMe, Facebook, Twitter, MySpace--is available in webOS, and developers of other services can add support via plug-ins. Then the system, as well as other apps, can use that information.
One of the accessories you can buy for a TouchPad is the Touchstone Charging Dock, which wirelessly charges the TouchPad when it's set in the cradle. It's a cool and solid bit of hardware, but the software integration makes it even cooler. Once the TouchPad realizes it's docked, it immediately launches into "Exhibition Mode." Any developer can write apps that work in this mode, which passively projects information--clock, photos, calendar, Twitter stream, you name it--onto the device's screen while it's docked. Once you remove the TouchPad from the dock, the apps vanish. And if you have one Charging Dock at work and another at home, the device knows they're different and can be configured to run different Exhibition apps in either place.
Related to Touchstone are two other clever proximity-based technologies built into HP's webOS devices. To pair the TouchPad with a webOS Phone, you can actually just lay the phone down on the bottom of the TouchPad next to the home button. At least, that's how it's supposed to work--I had to do the Bluetooth pairing manually. There's also a "touch to share" feature that lets you quickly transfer data (such as a web page URL) from one device to the other via a tap, but I couldn't get that to work either. Oh well.
I especially appreciated webOS's app-switching interface. Tap the hardware button (or run a finger from off screen to on) and the app you're using pulls back, becoming one card in a strip of cards arranged horizontally. Each card represents a running app (or a set of related app windows), and you can swipe backward and forward to pick which app you want to use. Flicking a card upward causes it to fly off the screen, quitting the app.
It's a far more intuitive system than Apple's, which requires a double-tap to invoke an icon-only app switcher, and to quit an app you have to tap and hold, then press an X. (I'll grant you, Apple's approach to app closure is to make it for emergency use only, while webOS encourages the user to open and close apps directly. When a lot of apps were open on the TouchPad, things could get poky, but like iOS, webOS is not shy about putting apps into a hibernation state when it's running short of memory.)