Popular stencils
Cisco CVD 2014 Healthcare Icons
Cisco released updated CVD Icons in many formats, but of course, no Omnigraffle stencil. These are built from the PNGs. http://www.cisco.com/c/en/us/solutions/enterprise/design-zone-smart-business-architecture/cvd.html This is the Healthcare Icons section.
Windows 8: Forms
Forms for Windows 8.
Variability Diagram
The variability model notation is a notation which has been proposed by Klaus Pohl and provides elements for modelling variability in SW products.
iOS Components for China
Are you designing mobile apps for the Chinese market? You can use this stencil to make beautiful wireframes for your mobile apps. Just drag and drop to create professional deliverables for your clients, developers, or team members. iOS 组件库：产品经理可以用来构建线框原型。使用此模板你不仅可以快速通过拖拽构建专业的手机 app 原型，也可以轻松地向你的客户和研发团队进行展示。
Java App Server Logos
These logos/icons were made for use in diagraming enterprise java application environments with non-heterogenous architectures.
McAfee Endpoint
McAfee labeled stencil for creating McAfee diagrams in OmniGraffle.
A/V Switching Components (Incl. Spyder, Encore, SP2)
This is a collection of common audio visual switching components including the Vista Spyder, Screen Pro II, and Encore.
Entity Relationship
Entity Relationship models for design database diagrams.
RabbitMQ
Another take on RabbitMQ and AMQP stencils with all vector graphics.