Routing not recognizing method

I have a very simple routes.rb:

... do |map|
  map.resources 'tags'
end

But going to localhost:3000/tags yields:

ActionController::MethodNotAllowed

Only get and post requests are allowed.

Relevant gems: * actionmailer (2.1.1) * actionpack (2.1.1) * activerecord (2.1.1) * activeresource (2.1.1) * activesupport (2.1.1) * fcgi (0.8.7) * mongrel (1.1.5) * rails (2.1.1)

Rails is vendored to 2.1.1.