Qt includes a set of examples that cover nearly every aspect of Qt development. They aren't meant to be impressive when you run them, but in each case the source code has been carefully written to illustrate one or more best Qt programming practices.
You can run the examples from the Examples and Demos Launcher application (except see QML Examples for special instructions for running those examples). In addition, Qt Creator can directly run these examples through the Welcome Page.
The examples are listed below by functional area. Each example listed in a particular functional area is meant to illustrate how best to use Qt to do some particular task in that functional area, but the examples will often use features from other functional areas as well for completeness.
These examples are provided under the terms of the Modified BSD License.
Qt Quick Example Code
The QML Examples and Demos site has a dedicated page for QML examples.
Qt Mobility Example Code
The Qt Mobility Examples page lists examples that show how the Qt Mobility APIs might be used.
Qt Examples by Module or Technology
Using ActiveX from Qt applications.
Doing animations with Qt.
Using D-Bus from Qt applications.
Integrating your Qt application with your favorite desktop.
Using Qt's standard dialogs and building and using custom dialogs.
How to access your platform's native drag and drop functionality.
Gesture programming examples.
Using Qt to manage and interact with a large (potentially) number of graphics items.
Adding interactive help to your Qt application.
Inter-Process Communication with Qt.
Using the model/view design pattern to separate presentation from data.
Using Qt's layout-based approach to widget management.
Building applications around a main window.
Audio, video, and Phonon with Qt.
How to do network programming in Qt.
Accessing OpenGL from Qt.
Accessing OpenVG from Qt.
How to use the Qt painting system.
Building UIs with QML
Using Qt Designer to build your UI.
Using Qt Linguist to internationalize your Qt application.
Using the Qt scripting environment.
Using Qt in Embedded Linux.
Using the document-oriented rich text engine.
Accessing your SQL database from Qt.
Using Qt's finite state machine classes.
Threading and concurrent programming in Qt.
Using Qt's containers, iterators, and other tool classes.
Using Qt's touch input capability.
Using the QtUiTools module.
Using WebKit in your Qt application.
Lots of examples of how to use different kinds of widgets.
Using XML with Qt.