, notable for being open source and... uhm, nothing else. Designed to be totally useless right after installation, unless the user modifies it into something (somewhat) usable. Seriously, it was designed not to do anything at all when installed. The user is the one who must try and make it usable by adding functions, modules and that kind of stuff, all by himself,
And even after that, your site will be fugly as hell, with totally generic content blocks (all drupal sites look like the spread firefox site, it uses drupal too), a horrible forum with too little options, plus your site will crawl like it's has an anchor tied on it's right leg.
The only reason people will use drupal is either because some open source junkie told them it's cool and awesome (wrong), or because their boss will fire them if they don't.
See: Wordpress on steroids