Listed below are some helpful websites and links that I use all the time to do WW II research.

English language

Soviet Army (RKKA) in World War II. http://www.armchairgeneral.com/rkkaww2/.

Axis and Allied forces in World War II. https://forum.axishistory.com//.

Maps and Aerial Photos from World War II. http://www.wwii–photos–maps.com/index.html

Site devoted to the Battle for Stalingrad. www.staldata.com.

Site devoted to the Battle for Stalingrad. www.stalingrad.net.

Russian language

Raw materials about RKKA in the World War II and before. http://www.soldat.ru/.

Soviet/Russian Military Books and Memoirs. http://militera.lib.ru/.

Military Maps of the Second World War and info about the Red Army.  http://www.samsv.narod.ru/.

Photo Archives

RGAKFD Archive – Russian Photo Archive. http://photo.rgakfd.ru/generalSearch.do

Das Bundesarchive – German Federal Archives. http://www.bild.bundesarchiv.de/index.php?barch_item=en_agb

Useful Translation Software 

Google Translate. https://translate.google.com/