A very general site that maps Library of Congress Classification to the Dewey Decimal Classification is LC to DDC is Map LC (LCC) to Dewey (DDC) Classification.

The site has not been updated since 2003, however, it can be useful to point to the area of Dewey needed. It also has link to the reverse: DDC to LC.

I have found the three volume Conversion Tables by Mona L. Scott to be more helpful. It also is a little dated (2006), however, it generally gets me the right area of Dewey.

If you know of a another or better resource please share by commenting.