SgmlReader was a source reference assembly from Microsoft which allows parsing Html as Xml -- that is, it takes poor, and even invalid Html and converts it to XHtml and gives you an XmlReader or XmlDocument from it.
An Open Source media-tagging library with support for ID3, ASF, APE, Xiph, and other media tags embedded in everything from .asf to .wv including mp3 and mpeg4, wmv, etc.
Supports a large variety of movie and music formats and abstracts away the differences so you can just write: file.Tag.Title, file.Tag.Duration ... etc.
There are are a couple of valuable tricks already in this toolkit:
1) a fix for NUnit (and others) to allow unit testing things which must run in STA mode.
2) a way to make your XAML data binding testable by tracing data binding warnings
OAuth.net is a .net library which provides full OAuth consumer and provider support. The library facilitates secure API authentication in a simple and standard method for desktop and web applications.
A sample project to implements a custom chrome with a UI similar to what Office 2007 does with its caption area... Basically achieves the effect, respecting the Theme chrome, and providing the same (not quite right) right-click menu on the caption as Office 2007 does
PostSharp Laos is a post-compiler, MSIL injecting, high level aspect oriented programming weaver. It looks amazing, and has been integrated with the .Net Enterprise Library 3.0 via the Enterprise Library Contribution project.