Pixate is a free platform for creating the user interface of native mobile apps with CSS. It is actually a graphics engine that transforms CSS into scalable graphics, bitmap effects and more.
Teehan+ Lax has created a very nice iOS7 GUI set so that anyone can easily design for this new version and it is shared for free.
Cardinal is a small and mobile-first CSS framework that positions itself as a starter-kit, provides the basics and lets the users customize/develop the rest.
Apple announced iOS7 and this new version of the OS seems to be coming with many changes regarding the interface,.
Swiper is a beautiful content slider that is built for mobile and works pretty fast as it uses hardware accelerated transitions.
Retinize It is a set of 2 free Photoshop actions where one of them slices the selected layer (or group) and the other for slicing + scaling it by 200%.
DeepTissue.js is a library that removes such differences (of MSPointer, WebKit Touch and mouse pointer APIs) and provides a cross-browser gesture handling library.
Mobile_Detect is an open source PHP class for detecting mobile devices.