Mega Blitz is a set of free wargames rules for operational level games set in the 20th Century.
Land and Airborne Assault are a set of free wargames rules that cover warfare from 1950 to the present. From the website:
Land and Airborne Assault is published in PDF format, is printer friendly and suiteable for all micro armour scales.
Land and Airborne Assault rules cover warfare from 1950 to the present day.
They include Electronics, Engineering, Artillery and Aircraft support plus Special Forces
and RPVs. The 4th edition has improved CAP air to air combat rules.
Pre-Game rules allow you to carry out a reconnaissance, flanking attack, sabotage and assassinations.
The morale reactions reflect actions troops and units would take on the modern battlefield.
Some dice rolling normally associated with modern warfare rules have been simplified making it possible to played a large game in a afternoon or evening.
Data specific to these rules for AFV armour class’s, size and speed, ATGM speed, generation and size, Aircraft size and payload and Artillery ranges is supplied on this website in the data and information section.
Edwardian Splendor is a set of free wargames rules for playing games with 54mm figures.
Ross MacFarlane offers a set of set of free wargames rules for the late 19th/ early 20th centuries called Sending MacDuff to the Front.
The Dice Flew Furiously is Ross MacFarlane’s set of rules for modernistic warfare. From his notes:
Notes: This is a simple set of rules for playing wargames in the Age of the Machine Gun. They are meant to provide an enjoyable game and to be evocative of stories told rather than an accurate simulation or recreation of experience or fact. More specifically, they aim to work in OSW fashion, not worrying about consistent time and ground scales and operating on multiple levels at once. Figures and vehicles are treated more or less as individuals so a player can get that emotional feel of being there in the midst of things while putting dozens if not hundreds of toy soldiers on the table and getting the feel of commanding a “battalion” or even a “brigade”, yet still be able to finish a game in 2 to 4 hours. The rules are intended for use with individual figures of 20mm size or larger but it should be able to be used with multi-figure bases either counting each base as a figure or by marking hits.