The Open VRML Advancement league has begun using libVRML97 as a serious basis for cross-platform supported VRML development. Weekly irc meetings, CVS access to the latest in developer code, and an actual Mac port have me feeling good about the direction these fine people are heading. Now being maintained by John Stewart. Geometric surface viewer that renders VRML scenes. This one has some beta code available.
New version is quite good.
Systems In Motion. Here's a chat client for VRML avatars. Here's the documentation tarball. Very early effort at an independant VRML viewer for Unix. This monster can Import from more 3D file formats than I can readily recall, and it exports to several as well.