Download Pharo or Squeak and start playing with it. Both (iirc) come with tutorial stuff. Or, if your feeling more adventurous, try Glamorous Toolkit (gtoolkit.

Download Pharo or Squeak and start playing with it. Both (iirc) come with tutorial stuff. Or, if your feeling more adventurous, try Glamorous Toolkit (gtoolkit.com) which comes with has tons of teaching material (in the tool itself) -- also well worth investing some hours in watching some of their videos.