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There is the following, though it is by no means complete.
The Manuscripts Division of the William L. Clements Library, University of Michigan has some muster rolls as well as other collections related to Hessian involvement.
The Marburg School of Archives in Germany has produced the book Hessische truppen im Amerikanischen Unabhängigkeitskrieg (Hetrina) : Index nach familiennamen which is available through a variety of book stores and libraries.
See also the sources listed on the following pages.
For a more general history, see the following: http://www.americanwars.org/american-revolution-hessians.htm