So what's the best IDE? If you're an eclipse user, it's Scala IDE (http://scala-ide.org/). You can find a full download eclipse + Scala IDE plugins on the typesafe homepage (http://typesafe.com/stack/scala_ide_download). If you're an IntelliJ user like myself you just need to install the Scala plugin.
Both IDE's have there drawbacks, none is perfect. I guess the easiest way to start is using the Scala IDE.
To test your new Scala skills you may want to solve some puzzles (http://scalapuzzles.org).
Have fun!
I haven't found any Scala IDEs stable or enjoyable yet. I've been using [insert favorite editor] with sbt[2].
[1] http://www.codecommit.com/blog/scala/roundup-scala-for-java-...
In short: thank you, bravo, and encore!
Best IDE: IntelliJ community edition (free) + Free Scala plugin http://www.jetbrains.com/idea/