Multimedia social-networking site

I'm working on a new site which is a social networking site based off of multimedia. The general idea is to create a place where people who specialize in a certain part of multimedia (ie web desgin) can interact with others who specialize in something similar (ie css master). So the person would come to the site, and submit their web design because they would like to see how it looked in a web browser. The person who is the css master and is not very good at web design can then take that image and convert it into css. Another example would be someone who does 3d modeling but do not have the skills to animate or texture the object. Once they are done they can submit what they have done to the file back to the website for everyone to see.

So now i have a couple questions. Does anyone know of any other website that does this? Second question is I plan on making the foundation of the site in Joomla, does anyone have suggestions for modules or components to use? And finally I was wondering how one might group together these cagetories this i what i have but not sure if it would make sense to everyone:

Stock Video/Photography- Landscape, portrait, B/W

Programming - Java, javascript, php, AS, ASP....

Graphics-print, logo, web design, drawing, vector....

3d/motion graphics-after fx, combustion, apple motion, maya, 3ds max, sketchup...

web-html,css,xml,wordpress,joomla...

Does this layout of categories make sense or would you arrange them another way?

Thanks for the help!