Tridiv - Web-based editor for creating 3D shapes in CSS
LibHunt - LibHunt tracks mentions of software libraries on relevant social networks. Based on that data, you can find the most popular projects and their alternatives.
iMeshup - Import, edit and share your 3D projects via web and mobile
AlternativeTo - AlternativeTo lets you find apps and software for Windows, Mac, Linux, iPhone, iPad, Android, Android Tablets, Web Apps, Online, Windows Tablets and more by recommending alternatives to apps you already know.
MR Builder - New way to visualize your ideas
GitSpo - Measure & engage your open-source community