After 2 public beta versions, I just released RocketCake
1.0. It is the responsive website designer I've been working on recently, and it is free to use:
There is also a professional edition which costs 39 euro to keep funding further development, but you can basically do mostly everything with the free basic edition. It is also available now in the Mac App Store. Feedback was very positive so far, and people really seem to like it.