Germ’s World has a large number of 25mm modern buildings for you to download and use in your modern miniautures wargames.
Ok. This is neat. It’s a Java window that shows how fast one infected individual can destroy a population.
Zombie Infection Simulation v2.3
FireForce! is a set of free wargames rules for 15mm platoon level modern skirmishes.
De Bellis Vietnam is a set of DBA-based quick and dirty rules for wargaming Vietnam.
Here’s a one-page set of free wargames rules for the Chechen Conflict, with figures based on on stands.