stuttgart, heidelberg and munich - oh my!

Anybody know of fun, interesting, unusual, cool things to see and/or do in Stuttgart and/or Heidelberg, Germany? Jim and I will be there, but he'll be at a conference and I'll be looking for places to hang out and read/write. We'll also be in Munich, but we're there for Oktoberfest, which should provide plenty for me to see and do. Any recommendations? Things to avoid?