More Sample Databases and Free Datasets

As I prepared my previous post on SQL Server sample databases, I also came across sample databases for other SQL databases.

PgFoundry provides a couple of database samples for PostgreSql. Real-world applications such as OpenNMS also use PostgreSql.

For MySql, I found the AdventureWorks database for MySql on SourceForge. This question on SO also covers sample databases for MySql.

Of course, a lot of real-world applications use MySql as their datastore, such as Bugzilla, MediaWiki, WordPress, or Joomla.

One question on SO asked for freely available datasets, and one answer points to an amazing list of datasets available on the web.

Makes me wonder whether there exists a comprehensive list of freely available data, all tagged with hierarchical categories?