Freedom of speech in the world
The rules on free speech vary dramatically depending on where you are. One thing however is clear, the more freedom people have when it comes to what they can say the more democratic the society they live in tends to be. Unfortunately right now the countries that allow freedom of speech are in a significant minority to those that don't.
Freedom of speech is something that is supposed to be available to everybody regardless of where they live. The United Nations considers it to be one of the fundamental rights that all people should have. Since all member countries have signed the charter that makes this a right in theory freedom of speech should exist in all of these countries. In practice of course this is not the case. In fact the vast majority of countries do not allow for the freedom of speech. Even more troubling is that we are seeing more rather than fewer restrictions being placed on what can be said.
In general freedom of speech exists only in democratic countries. This is largely because freedom of speech is essential to have a properly functioning democracy. Unless people are able to get all of the relevant facts and make an informed decision democracy cannot work. That being said even in these countries there are limits on freedom of speech. Usually these limits are enacted in order to protect other rights like the right to privacy or to prevent hate speech. In most cases these limitations are considered to be reasonable for a democratic country.
Most countries of course do not have democracies, at least not properly functioning ones. In these cases there is almost always censorship on what can be said. Just as a democracy can't survive without free speech a dictator can't survive with it. The goal in this case is to limit what the people know about the government's activities in order to keep opposition to the government to a minimum. This is getting harder and harder to do as the recent uprisings in the Arab world have demonstrated. There are now just so many options for communicating that it is very hard to censor them all.
In some cases the censorship is not done primarily to protect the government to protect society. That being said most countries that do this also restrict what can be said about the government. This is most common in the Islamic world were many countries will censor sites that show things like pornography in order to help maintain social norms. This type of censorship is somewhat controversial as there are those who say that it is essential for society and others who say that it is wrong. In most cases the people who live in the countries that censor free speech tend to support the restrictions.