I've produced a 4 page document that provides a very concise summary of Python 2<->3 differences plus the most commonly used new Python 3 features. It is aimed at existing Python 2 programmers who want to start writing Python 3 programs and want to use Python 3 idioms rather than those from Python 2 where the idioms differ.
It uses Python 3.1 syntax since that looks like being the standard for a few years in view of the language moratorium.
The document is U.S. Letter size but will also print fine on A4 printers.
It is available as a free PDF download (no registration or anything) from InformIT's website. Here's the direct link: http://ptgmedia.pearsoncmg.com/imprint_downloads/informit/promotions/python/...
And of course, if you want more on Python 3, there's always the documentation---or my book:-) "Programming in Python 3 (Second Edition)" ISBN-10: 0321680561. -- Mark Summerfield, www.qtrac.eu