Ever have an awesome idea for an iPhone app but don't have the graphic design skills to build a good mockup to show off to potential partners? Well, put away your pencils and napkins and go check out Keynotopia.com. The site offers users templates consisting of thousands of vector user interface components that allow app developers to simply drag and drop components to form a mockup of their app.
The templates are in Keynote and PowerPoint format and allow you to easily create user interfaces. They also allow you to add user interactions and animations by adding hyperlinks or slide animations to various UI elements. What's more, after you've designed your app in Keynote or PowerPoint, you can export the file as a clickable PDF document and load it onto your iPhone or iPad to see how it would work as a real app.
Multiple templates are available across different platforms, and all templates sell for US$9, although you get discounts if you buy them in bundles. Besides iPhone and iPad templates, Keynotopia also makes templates for Windows, Mac OS X, Android, BlackBerry, Windows Phone 7 and Facebook apps.