I was looking for a way to convert a spreadsheet to LaTeX code today. Googling for a solution several links to various Excel spreadsheets with macros showed up, but they all seem to work only with Office pre-2004. Finally I found a useful web page that does a simple CSV to LaTeX table conversion. It would be nice to find a solution to converting a spreadsheet with some formatting, but at least this saved me the effort of setting up the entire table manually.
On my search I also came across a list of various useful LaTeX-related converters.