Auschwitz, Birkenau, Chelmno, Belzec, Sobibor, Treblinka, Maly Trostenets, Jasenovac, Majdanek, Sajmiste... (It's possible that I forgot to list some)

Amersfoort, Arbeitsdorf, Auschwitz-Birkenau, Banjica, Bardufoss, Bełżec, Bergen-Belsen, Berlin-Marzahn, Bernburg, Bogdanovka, Bolzano, Bredtvet, Breendonk, Breitenau, Buchenwald, Chełmno, Crveni krst Dachau, Drancy, Falstad, Flossenbürg, Fort de Romainville, Grini, Gross-Rosen, Herzogenbusch, Hinzert, Janowska, Jasenovac, Kaiserwald, Kaufering/Landsberg, Kauen, Klooga, Langenstein-Zwieberge, Le Vernet, Majdanek, Malchow, Maly Trostenets, Mauthausen-Gusen, Mittelbau-Dora, Natzweiler-Struthof , Neuengamme, Neuengamme-Alderney , Niederhagen, Ohrdruf, Oranienburg, Osthofen, Płaszów, Ravensbrück, Risiera di San Sabba, Sachsenhausen, Sajmiste, Salaspils, Sobibór, Soldau, Stutthof, Theresienstadt, Treblinka, Vaivara, Warsaw, and Westerbork.

There were Klooga,Vaivara,Treblinka,Sobibor,Chelmno,Belzec,Majdanek,Auschwitz,Plaszow,Neuengamme,Stutthof,Bergen-Belsen,Ravensbruck,Gross Rosen, Sachsenhausen,Mittelbau Dora,Flossenberg,Dachau,Buchenwald,Natzweiler,Mauthausen,Gospic,Jasenovac,and Sajmiste. I'm sure there are probably more but these were the known camps and were the worst there probably could be.

It is a misconception that Jews were the only ones in the camps. They did make up a large percentage of the population, but several other groups were imprisoned there as well. Gypsies, homosexuals, Jehovah's Witnesses, handicapped, and even those that were just not liked for political reasons were taken away. As far as when these people were released depended on what camp they were in, and when forces came in to liberate them. Not all camps that were closed were liberated. That usually meant that all the prisoners were killed or moved to another camp. Even at the camps that were liberated, there were often thousands of deaths. Here is a list:

Auschwitz: liberated January 27, 1945

Belzec: Closed without liberation June 1943

Bergen-Belsen: liberated April 15, 1945

Bogdanovka: massacred and closed December 31, 1941

Buchenwald: liberated April 4, 1945

Chelmno: liberated January 20, 1945

Dachau: liberated April 29, 1945

Flossenburg: liberated April 23, 1945

Gross-Rosen: liberated February 14, 1945

Janowska: liquidated after attempted uprising November 19, 1943

Jasenovac: revolt, 80 escaped, remaining 520 killed, April 22, 1945

Kaiserwald: liberated October 13, 1944

Majdanek: liberated July 24, 1944

Maly Trastsianiets: liberated June 28, 1944

Mauthausen-Gusen: liberated May 5, 1945

Neuengamme: May 3, 1945 closed and all 10,000 prisoners killed in a battle

Ravensbruck: liberated April 30, 1945

Sachsenhausen: liberated April 22, 1945

Sajmiste: Closed September 1944

Sobibor: successful revolt October 14, 1943

Stutthof: liberated May 9, 1945

Theresienstadt: liberated May 1, 1945

Treblinka: successful revolt August 2, 1943

Uckermark: liberated April 30, 1045

On 24 July 1944 the Soviets reached Lublin in Poland and found the destroyed, evacuated and burned out remains of Majdanek. In August they reached the abandoned camps at Sobibor and Treblinka.