I want to create a little video manipulation app. in .NET.  It has to
load/play/save video and do some basic image manipulation.  I want to avoid
commercial (ie. not free) libraries.  Does anyone have links to information
to get me started?  I'm very familiar with .NET/C# but have little video
coding experience.

I guess DirectX9 will do what I need?  I'm downloading the SDK now.

Any good resources for image effect & filter algorithms?  I want to create
pixelation effects, embossing effects, etc.

I believe you'll be wanting to research DirectShow:
http://msdn.microsoft.com/library/en-us/wcemultimedia5/html/_wce50oridirectshow.asp

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