With all the noise that Rails makes, you would be forgiven for thinking that it is the be all and end all of the Ruby world – sure it has popularised the language, but there are lots of other cool projects using the Ruby. Here are a few:
Merb is another full-stack web framwork, which works a lot like Rails. However, the author has stripped quite a bit of the fat away, and made the framework mush less opinionated as well as making it thread-safe. Rather than having a large monolithic core, Merb tries to be as modular as possible relying on third party gems for much of it’s functionality.
It includes support for different Object-Relational mappers (ORMs – the thing that mediates transactions between your application and your database), including DataMapper, Sequel and even the Rails default ORM: ActiveRecord.
Merb stands for Mongrel + ERB, so it isn’t suprising that they make up a significant part of the framework, although you can use HAML and SASS as your templating engine.
Camping is a micro-framework (only 4k!) designed by the disturbingly talented Why the Lucky Stiff. It is probably more an exercise is seeing how much you can do with little code, but it would be useful if you were throwing around a prototype or one-off site.
Also by _why, shoes isn’t a web framework at all – it is designed to let you easily program small desktop applications. _why has created a lovely little toolkit wrapper around the Cairo graphics library, which is going to be the basis of “Hackety Hack” – a beginners programming starter kit (think lego, but with code). Although still in it’s infancy (last time I checked it didn’t support gems) it can be fun to do some GUI programming every now and then – mainly to realise why you picked the web in the first place!
There are of course many more cool Ruby projects – why don’t you go and spend a couple of minutes trawling through rubyforge.com?