- Kendo UI wrappers for CSHTML5
- Chart controls (Plotly)
- JSON Serialization / Deserialization
- SignalR
- WebGL 3D / Three.js by rkmore
- Particles & Weather by TaterJuice
- Busy Indicator Spinner by Sesztak
- ZipFile
- DatePicker by TaterJuice
- TimePicker by TaterJuice
- Unofficial ArcGIS Mapping control (in progress)
More extensions, updates, and discussions can be found on the Extensions and Plugins section of the Forums.
You may also be interested to read: How to Create Extensions for CSHTML5.