Artsy - A global platform for discovering and collecting art.
Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
Chairish - Shop Chairish, the design insider's source for the very best in vintage and contemporary furniture, decor and art.
Anchor CMS - Free and lightweight blogging system
1stdibs - Antique and Modern Furniture, Jewelry, Fashion & Art
Textpattern - Textpattern is an elegant content management system that is free, open source software.