http://studio.bricklink.com/v2/build/studio.pageStud.io is BrickLink's Unity-built version of LEGO Digital Designer. It can import saves from LDD and other LEGO applications/formats (like LDraw), render your creations in extremely high quality (thanks to integration with POV-RAY, something digital designers have been using for years) and is connected with the BrickLink website so that you can easily buy your creations if you've got the coin and they have the parts.
Stud.io has been in closed beta for a while; it's a bit buggy and it doesn't have all of the parts or colours of LDD/LDraw just yet, but that inbuilt realistic renderer is loving sweet (normally it's quite a process to get your LEGO Digital Designer sets linked up with POV-RAY).
[Naturally, it's recommended you play with the POV-RAY settings to get it looking loving legit, I just did a quick render to show off the tech]
