Deathspike 

A light abstraction of HtmlAgilityPack implementing the minimal functions to work with Linq under most PCL configurations.

A tiny HTTP abstraction layer for PCL.

ImageTools for Silverlight made compatible with PCL.

A high-performance asynchronous object mapper for .NET 4.5/Mono 2.12 and higher.

A simple concurrent asynchronous NodeJS-inspired event loop for C#.

Difflytic creates and applies binary diffs, supporting multiple files and streaming diff access.