If you need to create either finished User Interfaces for Web sites and applications, or simply need to create a quick mock up of a user interface or interactive project, check out the User Interface Design Framework from Webalys. This is a free library of hundreds of icons, styles, and UI elements that you can use and modify in your projects. They are presented both as Illustrator files that you can open, and as handy Illustrator Symbol panels. These elements can be used in Illustrator CS2 or newer. [via John Nack].