There is a 'Ruby on Rails for Dummies' book. I don't know how it
stacks up against
the competition, but if you are a fan of the 'Dummies' series you
should possibly
look it up.
I find the Ruby Cookbook handy to mine for examples of when I need to
get something
done but don't personally know how - most of the tasks can be mapped readily to
something that you need to do directly - its a great book. I don't
know if the Rails
Cookbook is as good, haven't read it, but the Ruby Cookbook can be used with
little Ruby knowledge, whereas I presume that some familiarity with Rails is
desirable to get most use out of the Rails cookbook.
http://pine.fm/LearnToProgram/
Has code examples and little exercises, and is very helpful, with a nice
progression.
Great writing style. I am teaching my Dad & girlfriend how to program with it.
Though it is a generic programming book, with Ruby as the instruction language.
Not exactly a Ruby primer, but it is dead cheap, and it does eventually
introduce you to Ruby concepts like blocks etc. I would imagine that this
book is probably the best at this. The elegance of using many of these Ruby
structures probably hides just how sophisticated they are.
http://poignantguide.net/ruby/
With foxes and crunchy bacon 'Nuff said

Seriously: It is quite good, but the style isn't for everyone.
It is odd, I will give it that. The style wasn't for me, but it is
free, and pretty
thorough. The Little Book of Ruby goes more basic (assumes nothing on
the part of the reader) and is another decent choice.
http://www.ruby-doc.org/docs/ProgrammingRuby/
The "PickAxe" as free online book, although it is only the first edition
The second edition is worth picking up anyway
As to the programs needed to write a Ruby script: A text editor is
enough. Everything else depends on a number of variables (like taste,
preferred OS, required features, etc.)
The Ruby install comes with 2 editors: FreeRIDE, which has a pretty
comprehensive
feature set, but I find it buggy and it crashes often for me. It also
comes with SCITE
which is a good editor.
On windows I really like the interface of Notepad++ (damn fine generic
windows editor
too) but it doesn't execute Ruby scripts within it (or I haven't
figured out how). For
Rails stuff I like RoRed, its got a nice balance of features.
I tried the various Ruby extensions in eclipse, and found them quite
buggy. RadRails
gets a lot of attention, but apparently it is best used in its
standalone UI form, and
not in the eclipse plugin form. Its also dependent on the Ruby module
for eclipse
which I have had issues with (it loses track of block 'end' statements).