kfrancis 

Chargify.NET is a comprehensive .NET API wrapper library for accessing Chargify.com, using XML or JSON to read/write.

Chargify API V2 .NET Wrapper

Rhino.Commons

A comprehensive C# API wrapper library for accessing Geckoboard.com, using XML or JSON to read/write widget data easily using strong-typed models

Injectable file adapters

.NET wrapper for Wistia's API

An implementation of http://email-invoice-format.org/ for .NET

An NLog target which lets you log screenshots

A script manager named script reference for Kendo

BugHerder is a comprehensive C# API wrapper library for accessing the BugHerd.com API

A C# implementation of ZModem protocol

A simple .NET API wrapper for Shopify