Google Code is a SourceForge-style hosting solution for open source projects: you can place your code in the supplied Subversion or Mercurial repository and document your project on the wiki. You cannot run code in Google Code, only download source code to share with others. It's free.
The Google App Engine is a shared cloud application site. You can host websites written in Python or Java, actually run the code on Google servers, with a cost proportional to use (it is free up to a certain amount).
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