gretlThis econometrics package is being written by Allin Cottrell of Wake Forest University. One of its unique features is that it is written under the "GNU Public License" so that anyone can redistribute or modify its source code (thus the full name: "Gnu Regression, Econometrics and Time-series Library"). Binary versions for Windows and Linux are available as well. While still in a relatively early stage of development, it offers many standard features: various least-squares estimators, Dickey-Fuller and Chow tests, etc. For inputing data, it can read RATS 4 databases and "comma separated value" files (most spreadsheets can save in that format). There is also a scripting language for gretl as well as an on-line manual.