If you like to create apps for iOS (iPad, iPhone) you can use the Xcode platform. The programming language of iOS(and Mac OS) is Objective-C. You can develop in C or C++ as well. Cocoa is the application programming interface (API).
You have one more excellent option – you can program apps for iOS in HTML5.
MonoTouch will allow you to use any .NET language and develop for iOS.
The officially supported integrated development environment (IDE) is Eclipse.
Additionally, developers may use any text editor to edit Java and XML files, then use command line tools (Java Development Kit and Apache Ant are required) to create, build and debug Android applications.
You can develop Android apps using HTML5.
The main tool you will use is Visual Studio (and Expression Blend). You can develop in HTML5 or XAML & C# or XAML & VB or XAML & C++.
The main tool you will use is Visual Studio (and Expression Blend). You can develop in XAML & C# or XAML & VB or XAML & C++.
BlackBerry development is done in Java and you can use the Eclipse envoironment.