Problem
You are trying to use rspec with Ruby on Rails 2.3.10, but although you install the rspec and rspec-rails gems you get the following error when you try to run script/generate rspec
Couldn't find 'rspec' generator

Solution
It turns out that there is a problem with the versions used, so by following the instructions for Rails >= 2.3.10 from here, you should be able to install the plugins and use rspec:
ruby script/plugin install git://github.com/dchelimsky/rspec.git -r 'refs/tags/1.3.1'
ruby script/plugin install git://github.com/dchelimsky/rspec-rails.git -r 'refs/tags/1.3.3'
ruby script/generate rspec

where the last tag (1.3.3) should be the latest tag for each gem.

*** NOTE *** If you get an error like :
You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.map (NoMethodError)

uncomment the following line (line 11) from features/support/env.rb:
require 'cucumber/rails/rspec'
and run rake cucumber again.