I just saw that whitehouse.gov is using drupal as a CMS and portal technology. One of the advantages of drupal seems that it is easy to add plugins and that programming is minimum, i.e. that re-inventing the wheel is at minimum. That is actually exactly the DRY philosophy of Ruby-on-Rails. So:
Quite subjectively, I find the Drupal administration interface a bit clunky. You can try it out for yourself without actually installing Drupal at opensourcecms.com. That being said, there seem to be a great momentum in Drupal community at the moment, and it's starting to become a really full-featured CMS.
Comparing Rails to Drupal is somewhat like comparing apples to oranges. Rails is an application framework and Drupal is a CMS (although with a kind of application framework included).
I'm a Rails developer so I'm all for Rails solutions but presently there is no Rails CMS that comes any close to a CMS such as Drupal in terms of functionality and plugins.
I attribute this partly to the 'less is more' philosophy advocated by 37signals.
Wordpress, Drupal, and others go for 'as many features as possible' and doing such end up attracting masses of users who will find that these products do answer their needs.
I've been playing with the idea of, like many others, starting a Rails based CMS system with plenty of features and a good plugin architecture. No time to work on this yet though between client work and development of an hosted application I'm working on.
allesklar, what is wrong with the extension system within Radiant? There are plenty of Rails CMS out there already. I suspect contributing to an established system to improve it would be more productive for the community at large than creating yet another niche CMS.
What are the drawbacks of drupal?
This is really a quite subjective question in relation to Ruby and Rails. Drupal is a solid content management option and really shines for community-oriented sites. It is useful for general purpose content management for non-portal sites as well. The drawbacks would be that it is built on PHP, if you are a Rubyist then that is a significant drawback. Additionally it is a beast of a project if you are looking at just the core. The API is quite large which is fitting for a project like Drupal, but this can make getting substantial customization done into a lot of coding work. Also, because of the whole architecture of Drupal there is no clear separation of data types unless you write a custom module that makes a clear separation and while this is in keeping with the "Drupal way" it is a little odd to some to think of EVERYTHING as a node or within the structure of Drupal's Taxonomy system or the like.
The biggest drawback to Drupal really can be best summed up this way: in order to make effective use of Drupal you really need to know and understand Drupal in a way that you don't for a CMS system like Radiant; but Radiant is nowhere near as complex as Drupal.
What would Rails or other Ruby based technologies disqualify as portal technology for whitehouse.org (or other CMS portals) ?
Rails is rather dissimilar from Drupal in that it is not really a content management system at all but a more general purpose application framework. You can use Drupal in ways similar to Rails, but Drupal is really much more than what Rails is. Better comparisons could be made between Drupal and say Radiant or BrowserCMS or some of the other Ruby/Rails CMS packages. There are Ruby/Rails portal systems out there but few match the bulk of Drupal and it's community. The most comparable options in the Ruby ecosystem only match bits and pieces of what Drupal can do, but that is because Drupal is that massive a project and a community. Drupal is a swiss army knife plus some for doing sites on the web. Ruby doesn't have a truly similar project out there because most Rubyists don't see any reason to duplicate Drupal's girth.
I would recommend the following projects as things to look at if you are considering use Ruby in place of Drupal (most of these Ruby projects will cover less than Drupal but fit closer with your site's actual needs):
If you are looking for portal technology built in Ruby, a relatively new candidate to consider would be EngineY. EngineY was originally built as a social networking framework but also has features that make it a viable candidate as a traditional portal. EngineY's concept of a 'widget' is similar to a traditional portal's portlet. There is a Managed Content widget included with EngineY that lets you create a portal made up of managed content. Best of all is that EngineY is very actively maintained and is evolving and improving daily.