Clutter (toolkit)
Clutter is an open source graphics library for creating hardware-accelerated user interfaces. It relies upon OpenGL (1.4+) or OpenGL ES (1.1 or 2.0) for rendering, can be compiled on different platforms (X11, Darwin and Win32) and has multiple bindings to other languages (including Mono, Perl, Python, Ruby and Vala). It also supports media playback using GStreamer and 2D graphics rendering using Cairo.
Clutter was created by OpenedHand Ltd, now part of Intel. Licensed under the LGPL v2.1, Clutter is free and open source software.
Read more about Clutter (toolkit): Programming Languages, Platforms, Design, Animation, Interface Builder, Integration Libraries