view3dscene (great)Displays many formats: VRML, X3D, 3DS, MD3, Wavefront OBJ, Collada. Open source, stable, small, quick, fast even on cheap hardware. Easy to install under recent Linux distros. I'm using SVN version and works under 64 bit linux too. I maintain the Arch Linux package. Only one con: it's not a browser plugin.
FreeWRL and OSX poor support (not recommended)I downloaded FreeWRL for OS X and installed it for using with Safari. The first simple demo I ran was this grey cone.
At the time I was writing there are some annoying bugs: when I open a WRL file in a tab all other tabs in the same windows became black and are thus unusable. This also happens when a VRML scene is embedded in page. Scrolling doesn't work the way it should as well. Another limitation of FreeWRL is that can only have 1 active window in Safari.
First I lived with it by always opening WRL files in a new window. Then I decided to use the FreeWRL application for all testing and development and return to Safari only for a final test. Fortunately in FreeWRL menu there is a File/Reload option. Also make sure to enable the Console Register under Window. Hope Safari support will be better in the future.
But even the FreeWRL application is unstable and slow. This may be because FreeWRL is Java-based :-P This is also why I don't use it anymore.
PS: When you make a mistake in a WRL file you will hear a female voice from FreeWRL actually speaking (!) the error message. Cool at first, but after a a few repetitions of the same errors I've decided to mute the speakers and read errors using the Utility -> Console OSX application.