A port of common spreadsheet functions to XQuery by the FLWOR foundation:
http://sourceforge.net/apps/mediawiki/zorba/index.php?title=EXcel_Function_Library
Contains loads of useful functions, especially for statistics. It says tested with Zorba, Saxon, and eXist. By the looks of it they don’t use any proprietary XQuery, so should be fine in MarkLogic too.
