Standard Rails library

Is there a 'standard' (ie. managed) library of Rails plug-ins/
modules/extensions/etc.? (ie. a bit like Perl CPAN or PHP Pear, etc.)

What I am currently looking for is an authentication module. I visited but this just
seemed to contain whole 'soup' of different bits of code with no easy
way to determine what each does or to judge which is more complete/

All the Rails plugins you could ever want can be found at Ben's site:

Lots of different authentication modules. Acts As Authenticated is
the most complete, but does need work in putting into your site.