Given the number of commenters who inaccurately claim "freedom of speech" as a legal right in Australia, I sometimes fear that knowledge of the basics of the US Constitution and its amendments is stronger than of our own. You can remedy your ignorance about those issues with Constitute, a new Google-backed tool that lets you search and compare constitutions from around the world.
The site lets you browse full constitutions (160 so far) in HTML and PDF form. You can also see the relevant excerpts around particular themes (such as freedom of speech or the role of religion), and search to find relevant excerpts. It turns out that just four countries identify a right to bear arms (Guatemala, Iran, Mexico and the United States) in their constitutions, for instance. Interesting stuff.