This is cool and works well (including the portable version) :[Wayback/Archive] webcamoid/webcamoid: Webcamoid is a full featured and multiplatform webcam suite.
Most code is C++ with bits using the QML language of the Qt cross platform UI library.
It reminded me of the Kylix days: the first Linux version of Delphi where the CLX GUI framework was a rework of VCL but based on Qt instead of Win32 GDI.
The downloads are at [Wayback/Archive] Webcamoid, The ultimate webcam suite! with installable and portable versions of 32-bit and 64-bit for Linux, Mac and Windows (I have tried the latter, see below why).
The Wiert Corner - irregular stream of stuff 