This article is about how to install Scala on Ubuntu. First off, you need Java installed. Scala programs compile to Java bytecode, which means you need the Java virtual machine in order to run your Scala programs. My advice is to install the sun-java6-jdk package. There are open-source Java implementations, but they suck. The Sun one is much better (the fact that it actually works is my main reason for using it).
Now the next step you might think is to then install the scala package from the Ubuntu repositories. Unfortunately as of today, that version is 2.3, and the most up-to-date one from the Scala pages is 2.7 (UPDATE Dec. 20/09: The version in the repo is 2.7.5 now, which is still not the latest version). You're much better off just doing this:
wget http://www.scala-lang.org/downloads/distrib/files/scala-2.7.7.final.tgzNow you have a working Scala implementation! Make sure to check the most up-to-date version on their website. I'll try and keep this up-to-date, but I'm only human and only check the Scala website every now and then.
tar -zxvf scala-2.7.7.final.tgz
sudo mv scala-2.7.7.final /usr/share/scala
sudo ln -s /usr/share/scala/bin/scala /usr/bin/scala
sudo ln -s /usr/share/scala/bin/scalac /usr/bin/scalac
sudo rm -rf /usr/share/scala /usr/bin/scala /usr/bin/scalac