PhoneGap
PhoneGap is (hopefully) the future of mobile phone apps. It essentially allows a developer to build a mobile app in one language (Javascript) and distribute it on major mobile platforms (Android, iPhone, Blackberry).
I've been playing around with the technology a bit. First off, it was quite a hassle setting up the development environment for the Android version of PhoneGap. The instructions page is huge! Also, the way you build and deploy an application is cumbersome because you have to type out a command in the command line that needs information like the location of the Android sdk. Then, once the project is built, you have to import it into Eclipse, whereupon you modify it some more before deploying to a mobile device.
I have a Droid, so I can test out the app on a real phone as apposed to an emulator. I can see that this technology can be extremely useful if you are trying to build and app for as many different devices as possible, but I also think that the "feel" of the resultant app isn't up to par with a normal mobile app. It feels as if you're on the web in a browser. For instance, on my Droid, in the web browser, web links show an orange border around them when clicked. The same thing happens in the PhoneGap app. I don't know if there is some way to disable that, but regardless I also think that the UI for a PhoneGap app would not look like a normal app's UI. In order for the app to look like an Android or iPhone app, you would need to customize the interface for each phone. In addition to these problems, PhoneGap does not currently support the complete functionality of all three mobile platforms. On Android, there is no contact support, for example.
What I'm saying is that this technology is too young for developers to begin migrating towards it, though I do think it is a step in the right direction. It is quite inconvenient building three separate applications with three different languages, so PhoneGap gives me hope for an eventual pseudo-uniformity among mobile platforms. We'll see if in the future, PhoneGap can change my mind.