Polaris UI Pack
The Polaris UI Pack is a set of beautiful UI components, which includes Edit Boxes, Check Boxes, Radio Buttons, Page Navigation, Menu, Buttons, etc. You can use this set in any of your projects, and even learn with it, by examining each component to see how it is put together.
Source: Smashing Magazine
Components are made in Adobe Photoshop using Shape Layers (vector elements). Therefore, you can increase or decrease the size of each element without any loss of image quality. In addition, the set contains 48 fully scalable vector icons with outline styles.
Source: Web Appers
It is a 6.88 MB download for the UI kit and another 5.95MB for the icon set. Definitely worth a download. It is free to use with no restrictions whatsoever.