I have never used these files, but after some googling i came up with this site which lists some vrml/x3d viewers. some people said that the InstantPlayer binaries works for ubuntu, but It wouldnt open some test .wrl i downloaded.
look like view3dscene works for some people. On this page you can find the binaries for both 32-bit and 64-bit Ubuntu.
It's a bit ugly, but seems to work for other users. Here is what it looked like for them: