test data

If you need a large database for experiments or a demonstration,
that I would recommend to use the IMDB database (http://www.imdb.com/interfaces#plain)
It contains around 30 tables, some of them contain around 2M entries.
There are foreign keys, keys.
The database is a set of plain text files, but it took 2 hours of my time to write perl script which convert it to Oracle SQL*Loader dump file.
The only problem is that you can not use this database for online demonstrations since data are copyrighted by IMDB.