A [previous question][1] revealed that there has been at least one (albeit minor) rules change for Uno recently.

This makes me curious to know if there have been any other changes to the rules over the years.

**How does today's Uno differ from the Uno of my youth?**  I'm only referring to standard Uno, not any themed version.

  [1]: http://boardgames.stackexchange.com/q/8436/40