Eastern front battles of World War II

1941 - Russian/German front: Information about Unternehmen Barbarossa, covering the advance on all the front sections
22 Juin 1941 - Barbarossa: Information in French about Unternehmen Barbarossa
Battle Of Leningrad 1941-1944: A detailed description of the battle for Leningrad, including interesting information about the Russian defenses
Kursk - July, 1943: The best website on Kursk on the Internet, with detailed information on everything from the equipment to the moons phases during the battle
Military History Online - WWII: Several articles about the battles and campaigns of World War II. Also includes articles on other wars
Military maps of WWII: Very good resource for maps of World War II
OnWar.com - Military History Research: Tanks of all major nations of World War II, maps of the battlefronts and a timeline of World War II, as well as several articles. Also includes information on modern-day AFVs and military history in general.
Operation Barbarossa revisited: A long article about Unternehmen Barbarossa, including view on the political background and aftermath
Stalingrad battlefield information: A virtual tour of Stalingrad, with both aerial photographs, maps and modern-day photographs
The Moscow Battle: The battle between German and Russia around Moscow between 1941 and 1942
The Russian Battlefield: A lot of interesting information about the weapons and battles of the Soviet Union during World War II
World War II Armed Forces - Orders of Battle and Organizations: Dr. Leo Niehorster's excellent website, with orders of battles for pretty much every country which fought in the war. His website also include errata pages for his books, and other interesting pieces of information
World War II day by day: Extremely detailed timeline of Germany during World War II, as well as many excellent articles, including a very large database of German vehicle markings
worldwar-2.net: Elaborate timeline of World War II, as well as many other interresting articles
WWII in Europe: Information and statistics about the European theater of operations