Charles Parcell has created a very slick set of stencils for website flowcharting that has just about every component you might use for a site, from Flash to PHP to .Net. And all of them in a unique, colored style. Awesome.
A handy set of isometric icons based on Visio's icons.
Advertising stencil from the Design Stencil kit in the Yahoo! Design Pattern Library.
This iPhone stencil includes various iOS user interface elements -- but every element is transparent so it can be used on any colored background to make attractive mockups for your iOS apps. Oh, did I mention that it's iOS7.
Charts and tables stencil from the Design Stencil kit in the Yahoo! Design Pattern Library.
Navigation and pagination stencil from the Design Stencil kit in the Yahoo! Design Pattern Library.
This stencil contains reusable shapes and elements for sketching wireframes or wireframing sketches whatever you prefer. This was done after realising that the sketch tools out there where quite closed in the elements they have and also its quite difficult to share your sketches digitally. You probably know what I am talking...more
More new major Omni application updates mean a new, cleaner, more Leopardy interface stencil. This one makes extensive use of tables, for maximum flexibility while maintaining pixel precision. Enjoy!
I use these characters lifted from http://www.google.com/googlebooks/chrome/ when I need to do a quick and dirty storyboard. Version 1.