Dependency injection is an implementation of inverse of control and can be used to increase program modularity and extendability. In general it also results in more testable source code.
There is a lot of dependency injection frameworks for bytecode based languages like Java and C#, for instance Guice and Spring. C++ lacks reflection facilities that make dependency injection so powerfull in these languages.
Injeqt is an attempt to build a powerful and reliable dependency injection framework on Qt's reflection based on MOC (meta-object compiler). For version 0.1 some basic features were implemented.