Many of the speeches that are popular today belong to specific categories, and are often made in response to specific occasions.
This is especially true in the political realm, where there are often established norms and formats when prominent politicians make their speeches. In the US, for example, two specific types of speeches include the inaugural address that newly elected Presidents make upon assuming office in January, or the yearly State of the Union address during their terms. Other examples include the victory speech that is delivered after winning an election, or the special Address to the Nation which is used in times of crisis (such as after the 9/11 terrorist attacks). Another common format is the announcement speech where a candidate makes it known that he or she will run for President.
There are also categories of speeches that do not belong directly in the political realm. One example is the commencement address, which is delivered to the graduating class of a university. These are sometimes delivered by celebrities or politicians, and often touch upon topics of national or global interest.
Finally, TED talks are also a popular genre that one might often be asked to work with in a school context. TED talks are intended to spread knowledge about a range of scientific, cultural or political topics, and often resemble a hybrid between a speech and a lecture. Although their main purpose is usually to inform, they often contain political messages as well.