ItsyBitsy is a project mainly written in Ruby, it's free.
Ironically not a web spider... A project I created to learn Rack and Git by replicating parts of Sinatra's functionality.
ItsyBitsy is a Sinatra knock off that's being worked on to teach me Rack and Git.
Currently it supports some of the Sinatra functionality and some other stuff I just wanted for the hell of it like folder functionality.
try it with 'rackup example/config.ru'