The Tranche Project uses hashes to insure that a dataset to which you link hasn't changed since you last consulted it.
Posted by
Peter Suber at 12/21/2007 09:13:00 AM.
The open access movement:
Putting peer-reviewed scientific and scholarly literature
on the internet. Making it available free of charge and
free of most copyright and licensing restrictions.
Removing the barriers to serious research.