xls to text converter
A quick search of apt-cache turned up the Ubuntu package python-excelerator for excelerator, which includes py_xls2html, py_xls2csv and py_xls2txt utlities. Will this work for you?
Your question reminded me of anti-word. I looked up and found anti-excel. I have never used it, so I can't vouch for how well it work or whether it makes achievable the task you have at hand. Also, I remember using a utility called 'sc' on linux to created spreadsheets on the console---though, I do not know whether it is capable of interpreting XLS files.