I had occasion to build a shell extension the other day to add a column to explorer's detail view.  I was getting all mired in the interop between the Win32 interfaces and such until I found this CodeProject sample.  Big props to it.  It's one of the finer CodeProject samples I've seen.  I thought this entry might send some more Google juice its way for other people looking to do shell extensions in the managed world.

Anyway, it was pretty easy after seeing a working version of all the interfaces and structures for the interop.  There's alot of tricky legacy stuff in there like interesting byte packing schemes.  Hopefully, with WinFX, this will be much simpler to do from managed code in the future.