The Extend Selection feature allows you to successively select expanding blocks of code so that you can easily select any expression in the code by placing the caret somewhere inside it and pressing Ctrl+WCtrl+Alt+Right or Ctrl+Shift+W a few times. Alternatively, choose View | Extend Selection.
Shrink Selection does exactly the opposite. Press Ctrl+Shift+WCtrl+Alt+Left or choose View | Shrink Selection.
For guidelines on how to configure this feature to take CamelCase into account, see CamelHumps.
This feature is inspired by and borrowed from JetBrains ReSharper, a developer productivity tool for Microsoft Visual Studio.