This is only marginally related, but it’s interesting, nonetheless: Mock Up My Tattoo. You choose a tattoo design or upload one of your own, upload a picture of yourself, and then they place the tattoo on your picture so you can see what it would look like.
MyDesignIn allows you to create an interactive floor plan and drag and drop bookmarked products into the design, but THEN you can collaborate with others online
ThinkCycle is non-profit focused on fostering open collaborative design. They have a shared online space for designers, engineers, experts, etc. to discuss, exchange and construct ideas towards the design of solutions for underserved communities and the environment.