Following the current poll, a tool like GL View should be a great one in the OpenGL SDK. This soft hasn’t been update since 4 months it’s too must according card evolution.
I don’t espect nVidia or ATI adding this kind of tools in the own SDK, an OpenGL SDK could be a great place for it.
PS: Maybe, we could use this post for an accurate answer of the current poll.
GL View is closed source correct?
I am planning on releasing my version of “GL view” called “The OpenGL Control Panel Application”. We can call it TOCPA 
I will GPL the source and need to spend time cleaning up the source.
screen shots here
Any chance we could get this cross-platform? 
Cross platform would be ideal but I don’t think it’s doable easily. I’m sure the MacOS and OSX is not a problem (for other programmers to do).
For Linux, I think there isn’t a standard control panel.
For now, it’s MFC and MS specific stuff.
Secondly, I need to make a installer so that it writes something in the registry.
Yes it is closed source… unfortunalty.
GL View provide a lot more than the supported extensions by the card. There is a catalogue of all graphics cards with their supported extensions.
Also, it give accurate features description, textures size, number of uniform, etc…
There is lot of tool like that, actually I done one for me before finding GL View. An other great one is HardwareInfos, http://www.ozone3d.net/hardware_infos.php but not as good yet…