CTAN, CPAN, RubyGem like

[Ary Borenszweig]

Deploying a Ruby on Rails 2 application is like this:

git clone ... (or hg pull ... or whatever you use)
rake gems:install (this installs all the libraries your project depend on)
rake db:create
rake db:migrate
rake db:seed

Very, very convenient. Otherwise you have to download the jars in you server, or
commit them to your source control which is pretty heavy.

In D, Java, C#, etc., it's a PITA, specially when your app depends on a specific
version of a library.