I've gone through posted topics here such as VRML and Active X plugins and even though porting to XP and such are valiant efforts what would REALLY be a huge step would be to have Celestia entirely web based.
VRML, as stated, is kinda dead and never got off the ground. Furthermore, to the common user, installing such a plugin is downright complicated so methink's Active X or even a java webstart app would be the key.
I'm currently working on budgeting/managing a huge multimedia site/tv documentary encompassing regional/national air/space flight subjects and am trying to encourage Open Source solutions the likes of Celestia.
Ultimately, we would like to have a browser's ActiveX control (seemless installation to common Win32/IE users) to a server-based installation of Celestia. To goal being to have both its space navigation as well as a GIS/topographic/sattellite pic terrain navigation (1) similar to genova (2)
1) Genova: http://www.genova.ch
2) A Genova implementation: http://www.sports-3d.com/
Having that said, if such endeavours are in effect at this time, I'd appreciate a few samples/links!

I'm also open to development discussions & theories that would get the project forward as I foresee much visibillity to Open Source communities the likes of Celestia in the aforementionned project.