Some free board games PDF's.

[Nathangun]

Here is a website that has free PDF's for board games, https://www.spigames.net/rules_downloads.htm

ASL & Bolt Action

 

[Gnarly]

Just got a copy of Butterfields D-Day at Omaha Beach last week........ ;D Not SPI, but a modern classic...

 

[Rico]

Must check these out -- look like a great resource.

 

[Nathangun]

Some more resources.

Company scale systems.
Sample Maps
The Battle for Austerlitz map, maybe not good for CM campaign game but still a nice map.
Some maps and rule books from Revolution Games
A collection of rule books of various game from GMT Games
Grand Tactical Series from MMP.
Hex and Counter from rpggeek.com
GMT VASSAL Modules.
Tactical Level games.