I am on Ubuntu,
Apache 2.2 Installed the fcgi via apt-get then removed it via apt-get remove.
Installed mod-ruby
configuration I added to Apache:

  LoadModule ruby_module /usr/lib/apache2/modules/mod_ruby.so
  RubyRequire apache/ruby-run
  <Directory /var/www>
    Options +ExecCGI
  </Directory>

  <Files *.rb>
    SetHandler ruby-object
    RubyHandler Apache::RubyRun.instance
  </Files>
  <Files *.rbx>
    SetHandler ruby-object
    RubyHandler Apache::RubyRun.instance
  </Files>

I have a file in the www direcoty with puts 'baba'
I have other files in that directory, all accessible via Apache.
Test file has been chmod 777
In the browser I get 403.
In Apache error log I get:

[error] access to /var/www/t.rb failed for (null), reason: Options ExecCGI is off in this directory

If I move this to a sub folder rubytest and modify the relevant config to be:

<Directory /var/www/rubytest>
        Options +ExecCGI
</Directory>

and making sure the directory has 755 permissions on it, it just try to download the file, as if it does not recognize the postfix *.rb any more

If I give directory and files 777 it fails:

usr/lib/ruby/1.8/apache/ruby-run.rb:53: warning: Insecure world writable dir /var/www/rubytest in LOAD_PATH, mode 040777 [Tue May 24 19:39:58 2011] [error] mod_ruby: error in ruby [Tue May 24 19:39:58 2011] [error] mod_ruby: /usr/lib/ruby/1.8/apache/ruby-run.rb:53:in load': loading from unsafe file /var/www/rubytest/t.rb (SecurityError) [Tue May 24 19:39:58 2011] [error] mod_ruby: from /usr/lib/ruby/1.8/apache/ruby-run.rb:53:in handler'

BUT, IF I USE *.rbx it works like a charm...go figure.