WebFX - plugin for Netscape 2.0
Windows 95/Windows NT Browsers:
WebFX - plugin for Netscape 2.0
Virtual Explorer - plugin for Microsoft's Internet Explorer
Other:
Dimension X's Liquid Reality - This uses JavaScript, so it's already compliant with any operating system, as long as you have a Java compliant web browser for your operating system. It is an internal VRML browser, and it is so far the only answer for Macintosh and Unix systems, since the others are predominantly Windows versions. It's still in production stages, though.
For ratings and more info, check out Stroud's CWSApps List of VRML Browsers for Windows 3.x and Stroud's CWSApps List of VRML Browsers for Windows 95/NT.