Building a backend business app? The Flakes framework looks like a great starting place for your interface designs:

Flakes is an Open Source Design & Frontend Framework that serves as a foundation for internal business applications. Flakes is a combination of CSS Libraries, JavaScript Libraries and Design files that serve as a foundation. Flakes gives priority to function and usability over glitz, it takes a no-nonsense approach to user interface design. ~ Flakes • An Admin UI & Template Framework