Let us begin by pointing out that a particularly bad topic for a school essay or paper is to argue about whether the Holocaust happened or not.
Whether it happened is not a matter of opinion; it did happen, and that can be verified to any reasonable standard of proof. Writing about how we know it happened might be interesting, or perhaps about the specific reasons Holocaust-denial is incorrect - but these are probably topics for a course in philosophy, not history.
For a school or college class, it is much better to pick a topic that allows you to interact with the information that you learn about the Final Solution. There are a lot of questions where there is room for legitimate debate, questions on which you can take a stand that seems right to you. Below we suggest a number of such topics.
Sophie Scholl, of the White Rose. Executed for anti-Nazi pamphleteering, in 1943, aged 21.
What gave the young German university students and medics involved in the White Rose the motivation and courage to oppose totalitarianism and genocide at the risk of their own lives? This topic gives you a lot of room to express an opinion and take a stand on just about anything, though you should talk to your teacher before straying too far into literature, society, culture, or current events.
For much of the general public, the unique horrors of the death camps overshadow the fact that about half the victims of the Holocaust were murdered by other means - worked to death, starved, shot. Yale Edeiken's essay on the Einsatzgruppen, and Ken Lewis's site provide an introduction. Another organization that engaged in mass shootings is called the Order Police. Christopher Browning's book Ordinary Men: Reserve Battalion 101 and the Final Solution in Poland is a good place to learn about the Order Police.
Though this topic would be good for a high school paper, it might not yield much room to pursue a thesis. Making people aware of uncontroversial historical facts they probably don't know about is not the same thing as arguing a position. You'd want to delve deeper into Christopher Browning's arguments (see below) to get to where you can express an opinion.
One real debate among historians is whether the mass murder of European Jews was planned by Hitler from before the war's start (intentionalism), or decided upon, as an alternative to forced emigration, during the war (functionalism). This makes a good paper topic because historians do not agree; there is a quite legitimate spectrum of opinion to explore.
Gord McFee's essay When Did Hitler Decide On The Final Solution? is an introduction to some recent contributions in this debate.
A very controversial book is Daniel J. Goldhagen's Hitler's Willing Executioners, which argues that centuries of antisemitic hate propaganda had prepared even ordinary Germans for the prospect of murdering their neighbors. The chilling conclusion is that the killers were not forced by the totalitarian Nazi regime or by the exigencies of war - they wanted to kill Jews and others they believed less than human.
As Christopher Browning's book, Ordinary Men: Reserve Battalion 101 and the Final Solution in Poland is one of Goldhagen's sources, it is interesting to examine why their conclusions are somewhat different. Browning believes the motivations of the murderers are a lot more complicated, but you will have to read his book to see how.
A recent book, A Nation on Trial : The Goldhagen Thesis and Historical Truth by Norman G. Finkelstein and Ruth Bettina Birn examines Goldhagen's sources and argues that Goldhagen's scholarship leaves a lot to be desired. There is certainly room within this topic to take a strong position, but consider whether you will be able to make a fully informed argument in the limited time and number of pages you have. Historians have spent decades investigating testimony, documents, diaries, letters, etc. on this sort of thing.
http://www.holocaustforgotten.com/ is a web site dedicated to the five million "other" innocent civilians killed by the Nazis in addition to the nearly six million Jews specifically targeted for extermination. As with #2, you might have a problem finding a sufficiently controversial thesis among the less well known facts.
The answer to the question, "Why do most people focus on the Jewish victims?" isn't really controversial. Reasons include: about 1/3 of the Jews in the whole world were murdered, while no more than 10% of any other group were killed; Nazi propaganda was specifically and virulently anti-Jewish; people who hold irrational hatreds of Jews today focus specifically on denying Jewish suffering during the Holocaust; and prejudice against some other victims of the Holocaust, such as Gypsies, the physically and mentally disabled, and homosexuals, is generally more socially acceptable today than antisemitism.
Fill in the blank: European Jews, German citizens, Western democracies, citizens of occupied countries, the Catholic Church or other religious groups.
The failure of the United States, Western Democracies, and non-governmental organizations including religion to intervene when informed of the mass murders is a complex but worthwhile topic. Another short essay discusses some of these issues. Clearly there is room for a strong thesis (one way or the other) here, but be very careful - the history and the issues are very complex, and people tend to get very angry and non-scholarly where religious and national motives are involved.
It might be safer to compare and contrast contemporary responses to mass killings in Cambodia, Rwanda, and Bosnia - many of us involved with THHP are very concerned with events there.
Many factors made the Holocaust possible, including: widespread respectability of "race science" and "race hygiene"; elimination of a democracy and its replacement with totalitarianism; prolonged war throughout the world; crushing economic hardship; isolationism in world powers; and poor knowledge of events in foreign lands.
Which of these factors might be likely to recur, and which seem most important? A book with a broad, thought-provoking sampling of writings on this question is Can It Happen Again? Chronicles of the Holocaust, Roselle Chartock and Jack Spencer, Eds., 1995.
A good website for learning about some of these issues is http://remember.org/educate/.
Photo of Sophie Scholl from An Honourable Defeat: A History of German Resistance to Hitler, 1933-1945, Anton Gill, 1994, p. 168f.
more short essays...