GPU Caps Viewer is a free and highly-featured tool that quickly describes the essential capabilities of your graphics card/GPU including GPU type, amount of VRAM , OpenGL API support level, OpenGL API extensions database and general system configuration, as well as a GPU-Stress-Test functionality (GPU-Burner). Furthermore, this software will allow you to view extensive reports in text or XML format.

Features:

quick view of the graphics configuration (graphics card / GPU type, amount of video memory, drivers version)

display of the main OpenGL capabilities (OpenGL version, texture size, number of texture units, etc.)

display of the OpenGL extensions supported by your graphics card or display of all existing OpenGL extensions no matter what graphics card you have. For each extension, you can open its description webpage available at the OpenGL Extension Registry or at NVIDIA's OpenGL Extensions spec. Very handy for graphics developers!

display of the system configuration: CPU type and speed, amount of systeme memory, operating system

GPU Burner: allows to make the GPU temperature climb in order to test the graphics card stability. You can actually open as many 3D views as you want in order to make your graphics card working to the maximum. For NVIDIA cards, the GPU temperature is also displayed.

list of links related to your graphics card: graphics drivers and graphics cards reviews. These links are regularly updated.

full report in text and XML format. This kind of report is useful for developers who needs an outline of the customer graphics system (for support purposes for example).