Vassal is a game engine developed by Joel Uckelman for building and playing online adaptations of board games and card games. You can use Vassal to play in real time over the Internet or by email. Vassal runs on all platforms, and is free, open-source software. There has been a decade long effort to make all Europa-games available in Vassal, which is pretty close to completion:
Link: Vassal Europa Homepage

Europa Games available for Vassal

Europa I – The German invasion of the USSR and the Soviet conterattack, 1941-1942.

Drang nach Osten (DNO). GDW 1973.
Fire in the East (FitE). GDW 1984.
Total War (TW) HMS 2012.

Europa II – The Eastern Front, 1942 – 1944

Unentschieden GDW 1973.
Scorched Earth (SE) GDW 1987.

Europa III – The Balkans Campaign, 1941.

Marita-Merkur (MM) GDW 1979.
Balkan Front (BF) GRD 1990.
Balkan Front Second Edition (BF2) GRD 2002.

Europa IV – The Norwegian campaign, 1940.

Narvik GDW 1974.
Narvik Second edition GDW 1980.
Storm Over Scandinavia (SoS) GRD 1998.

Europa V – The Battle of Britain and Operation Seelöwe, 1940.

Their Finest Hour (TFH) GDW 1976.
Their Finest Hour (TFH) Second Edition GDW 1982.

Europa VI – The Campaign in North Africa, 1940-1942.

Western Desert (WD) GDW 1982.
War in the Desert (WitD) GRD 1995. (Europa VI/IX/XI in a single publication.)

Europa VII – The German Invasion of Poland, 1939.

Case White (CW) GDW 1977.
First to Fight (FtF) GRD 1991.
First to Fight Second Edition GRD 1999.

Europa VIII – The German attack on Holland, Belgium, and France, 1940.

Fall of France FoF GDW 1981.

Europa IX – Operations in the Near East.

The Near East (NE or TNE) GDW 1983.

Europa X – The Spanish Civil war, plus Spain and Portugal in World War II.

Spain and Portugal (S&P) GDW 1984.
For Whom the Bell Tolls (FWtBT) GRD 1995. (Covers the Spanish Civil War as well.)

Europa XI – The Allied invasion of French North Africa, 1942-1943.

Torch GDW 1985.
War in the Desert (WitD) GRD 1995. (Europa VI/IX/XI in a single publication)

Europa XII – The Allied invasions of Italy and France.

Second Front (SF) GRD 1994.

Europa XIII – Expansion module giving a bigger picture of the Soviet war effort

The Urals GRD 1989.
Combined module for FitE, SE, and the Urals.

Europa XIV – The Soviet attack on Finnland, 1939-1940.

A Winter War (AWW) GRD 1992.

Europa XV – The Naval War.

Supermarina: Naval Operations in the Mediterranean Theater of Operations. By Winston Hamilton The Europa Magazine Issue 17
Naval Warfare Mediterranean: Naval module for Mediterranean. By Daniel T Shaw.
Naval Warfare Northern Europe: Naval scenarios for NE Atlantic, North Sea, and Barents Sea. By Daniel T Shaw.

Europa XVI – Grand Europa

The first Grand Europa module, links the games War in the Desert and Balkan Front with new material (maps and counters) covering the campaign for Italian East Africa.
Wavell’s War (WW) HMS 2005.

Glory Games available for Vassal

Glory I. War of Resistance, China 1937-41. GRD 1998.

Glory II. The Damned Die Hard, Philippines, 1941-42. GRD 1999.

Glory III. Samurai lightning, the Malaya Campaign. Unpublished

Glory IV. Vital Flank, the Solomons and New Guinea. Unpublished

Glory V. A Wet, Green Hell, the Burma Campaign. Unpublished

Great War Games available for Vassal

Great War I. March to Victory – West Front 1914-1916. GRD 1997.

Great War II. Over There. GRD 2000

Europa Scenarios in Vassal

War in the Outposts – The Europa Magazine.

Europa Czech 38 Czechoslovakia declines the Munich Agreement and so Germany invades. Europa: Nuts and Bolts magazine Issue 21/22 Nov 1987. The article is in the module under Help>Scenario.

Europa Austria 38 Austrian government had ordered the Bundesheer to resist the German takeover of Austria in 1938. “Austrian Army of 1938” by Michael Parker in Europa Nuts and Bolts issue 21/22, Sep-Nov 1987.

Nomonhan Khalkin Gol 1939 The border dispute of the summer of 1939 between Japan and the Soviet Union, over the Mongolia/Manchukuo border.