Nexus is a project that is, essentially, the Semantic Web meets Second Life (a virtual world).  Using Second Life, various ideas and concepts are being tested to visualize semantic data in 3D and how that data could be worked with and visualized collaboratively.  Collaboration is the main reason for doing this in Second Life and why Nexus is not just being done as a stand-alone 3D browser.  I'm very much interested in trying to make the Semantic Web more accessible to the average person.
For those of you who have been following my Monolith Project, Monolith will be absorbed by Nexus.  PDB data can be expressed semantically and thus be visualized using Nexus.  The added benefit in doing it this way is that other semantic data sources can be semantically linked and reference while searching for/or working with a particular structure(s).  In addition, since Nexus is driven by a SPARQL query engine, molecular selection criteria become more flexible by allowing a SPARQL query to be used to pick which parts of a structure are acted upon for display or modification.  Nexus is not limited to just molecular visualization but will be able to visualize various semantic datatypes (FOAF, DOAC, etc) from multiple data sources.  Much of Monolith's code base will be used since that project worked out many of the rapid rezzing issues that Second Life has, as well as, the interfacing between the virtual world and the real world.