Install Scala on OSX

gistfile1.sh

# to install the latest stable version:
brew install scala --with-docs

# to install scala-2.10.0-RC1:
brew install https://raw.github.com/gist/3939012/scala.rb --with-docs

# to switch versions (from https://github.com/mxcl/homebrew/wiki/External-Commands):
brew switch scala 2.9.2
brew switch scala 2.10.0-RC1

# to see which scala you're currently using:
brew which scala

scala.rb

# Recipe for scala-2.10.0-RC1

require 'formula'

class ScalaDocs < Formula
  homepage 'http://www.scala-lang.org/'
  url 'http://www.scala-lang.org/downloads/distrib/files/scala-docs-2.10.0-RC1.zip'
  sha1 '90ca287750facaf67515619f4378ff952872eb46'
end

class ScalaCompletion < Formula
  homepage 'http://www.scala-lang.org/'
  url 'https://raw.github.com/scala/scala-dist/27bc0c25145a83691e3678c7dda602e765e13413/completion.d/2.9.1/scala'
  version '2.9.1'
  sha1 'e2fd99fe31a9fb687a2deaf049265c605692c997'
end

class Scala < Formula
  homepage 'http://www.scala-lang.org/'
  url 'http://www.scala-lang.org/downloads/distrib/files/scala-2.10.0-RC1.tgz'
  sha1 '33ea297ee6c850bcf3b67525fc9df93b004ccd85'
  version '2.10.0-RC1'

  option 'with-docs', 'Also install library documentation'

  def install
    rm_f Dir["bin/*.bat"]
    doc.install Dir['doc/*']
    man1.install Dir['man/man1/*']
    libexec.install Dir['*']
    bin.install_symlink Dir["#{libexec}/bin/*"]
    ScalaCompletion.new.brew { (prefix/'etc/bash_completion.d').install 'scala' }
    ScalaDocs.new.brew { doc.install Dir['*'] } if build.include? 'with-docs'
  end
end

Thanks Charles for putting this up, this is very handy.
I've forked a version to use scala-2.10.0- RC5
Feel free to pull back those changes in.