The folks over at Yahoo! Developer Network have released another good resource for the web designer: the Yahoo! Design Stencil Kit. The kit contains 16 different high-resolution image sets (available as OmniGraffle or Visio stencils, PDF, PNG, and SVG). Each one has a batch of anonymous elements designed for use in mocking up web pages and other user interfaces. A few of the topics include standard ad units, form elements, iPhone user interfaces, tabs, placeholder text, and UI controls.
A good set of stencils – and this is one – allows you to focus on the overall layout and look of your user interface before you start writing code. The stencils include links back to YUI implementation code and pages from the Yahoo Design Pattern Library in some spots, but you can use them no matter what toolkit you choose. The whole thing is licensed under a Creative Commons license.