This list is incomplete and constantly growing. Help us making it bigger and better!

Gaming clubs:
Associazione Casus Belli
A.S.G.S. (Associazione Sammarinese Giochi Storici)
ASL Italia (official site for Advanced Squad Leader players in Italy)
Ass.NoFerPlei
Gilda dei Giocatori
Hydra Games 

Publishers
GMT games
MMP (Multi Man Publishing)
Acies Edizioni
Europa Simulazioni
Ventonuovo Games
Ares Games

Conventions and gatherings
San Marino Game Convention
Modena Play

Websites about board wargames
The Paper Army 
BoardGameGeek (a must for all board games’ lovers!)
Consim World
Grognard
Hexasim