This is a rip from http://www.barre.nom.fr/vtk/links-classes.html
Have you written your own VTK C++ classes on top of the VTK core ? Here are some of them, but feel free to send me any links to your own work : extending the VTK functionalities helps ! Don't forget to check: How to Contribute, the Coding Standards and the Copyright Information :)
(J. Shalf) "Use in place of a vtkRenderWindow to draw an offscreen image. This is specifically for Unix/OpenGL/X11 systems. [...] For SGI systems, it will use pbuffers for hardware accelerated offscreen rendering. For all other architectures, it will use GLX pixmaps which tend to be software-rendering (except for hardware-accelerated Mesa)."
 (Glen Lehmann) "Glen Lehmann has updated John Shalf's above code to work with more recent versions of VTK."
vtkHDFReader (J. Shalf) "HDF4 is a self-describing platform independent binary file format for storing Scientific Datasets. [...]. It also interoperates with the Unidata NetCDF standard. The vtkHDFReader is able to read HDF-SDS (Scientific Dataset) files into vtk as well as some versions of NetCDF data."
(J. Shalf) "This is a slowly growing collection of vtk filters that are being parallelized for Shared Memory Processor (SMP) architectures. The target audience is people who have very large datasets and computers with large numbers of processors and want to accelerate operations like streamlines and contour filters in order to maintain interactive performance."
(S. Desmet) The class vtkIVImporter is capable to import most VRML1.0 or Inventor1.0 scenes. The lex and yacc files come from an existing VRML1.0 syntax checker. Code was incorporated to generate the necessary vtk structures.
(M. Hall) "A small, fast orthogonal slicer for vtkStructuredPoints datasets. It has the following advantages: 1)There are no extents or odd things to set (it uses the dimensions of the input to determine the dimensions of the slice plane). 2)To use it, you set the input, set the plane normal (x,y, or z axes) and set the x,y, or z coordinate of the plane. 3) It has 2 modes of output: Triangle strips and Quads (actually, polygons)."
(M. Hall) "(Simple Multi Grid) This package is intended to make multigridded datasets (i.e. collections of native vtk dataset types, most importantly StructuredPoints ) into first class datatypes. Only a simple prototype is availible now, however the non-"Simple" version will have the ability to associate a structure with an MGDataset (For dealing with simple collections of boxes, AMR datasets, or hierarchical collections), thus allowing (specially written) filters to take advantage of any inherent structure in the data. Threading will be added at a later date. "
(CINECA) Various classes : Image Packing/Unpacking, Image Processing, Import/Export, Geometric Tools, Math.
CREATIS Gdcm -which stands for Gnu DiCoM- is yet another C++ library dedicated to reading/parsing and writing Dicom files.
* offer Dicom jpeg compressed image support, * enable Dicom header parsing of sequences and overlays, * distribute a VTK thin wrapper of gdcm (essentially a vtkGdcmImageReader).
wxWidgets (previously wxWindows)
wxVTK - Yet Another Port of wxVTKRenderWindowInteractor This class enable VTK to render to and interact with wxWindows just as any wxWindow component. wxVTKRenderWindowInteractor provide a VTK widget for wxWindow. This class was completely rewrote to have the Look & Feel of the python version.
(J. Ehrhardt) vtkQGL provides C++ classes to render your VTK data in a Qt widget. Surface rendering and volume rendering is supported, and now some classes for image display are added. Qt is a fully object-oriented multi-platform GUI toolkit.
(M. P. Pagey) This package contains two classes vtkQGLRenderWindow and vtkQGLRenderWindowInteractor which allow one to use VTK with the QGLWidget extension of Qt. In other words, these classes can be used to build Qt applications which utilize the facilities provided by the VTK libraries ; "It should work with both VTK-2.4 and VTK-3.1.2. It also has full GNU autoconf based installation. It does not use any X-windows specific code and hence should work with Microsoft Windows [...]".
(M. Koenig. ) The vtkQt classes combine VTK and Qt(TM) for X11.
(J. Stifter) This package combines vtk and qt together ; "The package is small and simple (800 lines of code), documented with doxygen, flexible to use (dynamic definitons, mouse button) and has been tested on win32, linux, SGI IRIX, IBM RS6000 AIX. It should run on every system, which compiles vtk and qt.".
(J. Shalf) "vtkFlRenderWindow extends FLTK's ability to embed OpenGL drawing areas into GUI's so that a vtkRenderWindow can be integrated with an FL user interface [...] The Fast Light Toolkit (FLTK) is a really nifty little cross-platform GUI framework which is complete with a little GUI builder called Fluid."
(C. P. Botha) "vtkFlRenderWindowInteractor is a VTK class [...] that enables VTK to render to and interact with your FLTK application."
(Sean McInerney) "vtkFLTK is a small C++ class library for development of FLTK event-driven interfaces for use with VTK. vtkFLTK bridges disparities between FLTK and VTK event and windowing system handling. Its use is made magically simple via VTK's Instantiator and Factory mechanisms as well as the CMake build system. See the copious examples for usage details."
(P. Rajlich, NCSA) "The idea is that you can compute geometry using VTK and render using Iris Performer. The advantage of doing so is that there are some things that VTK hasn't been designed for, such as rendering to multiple channels (i.e. multi-headed displays such as the CAVE here at NCSA). Using vtkActorToPF, you can write interactive visualization applications for such environments without much trouble. Performer is a Silicon Graphics rendering library that also provides other features not found in VTK such as scene-graphs and intersection testing."
(M. Hall) "This small collection of files enables one to display a vtkActor in a CAVE/ Immersadesk/ I-Wall, etc. with a very small amount of work. It is very stable, very easy to use, and has a built in shared mem. buffering scheme which means that you can use dynamic vtkActors without writing your own double buffering code. Caveats are that it does not yet support vtkCameras, Lights, or Texture Maps, but if there is enough demand, these features can be added fairly easily."
(shock8) "FXVTKWindow is a FOX-GUI renderering window widget class for the exceeding visualization library VTK."