Does anyone know if there is any fantastico or pre-installed software available with DreamHost packages? I’m considering signing up but have no idea whether what kind of software is pre-installed. Thanks.

DH has their own one-click installer for a handful of software packages. The knowledge base article about it can be found here:
You can use it to install WordPress, phpBB, Advanced Poll, osCommerce, and MediaWiki (though MediaWiki doesn’t seem to be mentioned in that article).