Ruby is a reflective, dynamic, object-oriented programming language, created by Yukihiro Matsumoto and released to the public in 1995. It is an extremely pragmatic language, less concerned with formalities and more concerned with ease of development and valid results. You will see Agile principles running through ruby and particularly with rails. Most of all TDD and BDD concepts / philosophies have been implemented for ruby developers. Ruby differs from most programming languages by syntax, culture, grammar and customs. It has more in common with LISP and Smalltalk than with most languages such as C++ and PHP.
If you can program in languages such as Perl, PHP, C or Pascal, using and learning ruby is quite easy, but the problem solving pespectives that ruby uses may throw you out at first.
The so popular and hyped ruby on rails DSL (domain specific language) is a framework for developing web applications and currently powers hundreds of large websites around the world.
Bioruby is an excellent bioinformatics library for ruby. Though not highly documented like its sister, bioperl, efforts are been made to improve its level of documentation. The bioruby community is also really nice and friendly. Not a single question that i have posted on the mailing list goes unanswered.
Hundreds of libraries for performing different tasks have been written for ruby , packaged as gems and hosted at rubyforge
So far my favorite ruby editor is the netbeans IDE, whose currently release is in beta 2. The final release is slated for 3rd of Dec 2007. (Am waiting!). It features auto completion, syntax highlighting among other cool things that makes programming a joy. It also comes bundled with the jruby release, a java implementation of ruby that is starting to rock the world, so you can choose to use either native ruby or jruby, the choice is all yours!
Ruby can be downloaded here