Dust Models offers a free digital version of their Dust 1947 rules.
Into Glory Ride Wargaming Rules
Into Glory Ride is a set of free wargames rules for battles set in the Renaissance and beyond. It covers the era 1500 – 1900.
DBA 3 Reference Sheet
The Society of Ancients offers a free DBA 3 reference sheet.
Undying Lands Fantasy Wargame
Undying Lands is a set of free wargames rules for fantasy battles. What’s interesting about these rules is that they ask players to base the figures as a “vignette” where the number of figures on a stand makes no difference.
Historicon Ancients Rules
Historicon is a set of free wargames rules for ancients miniatures. Alienstar Games bills it as a return the ancients games of old, featuring lots of figures, buckets of dice and army lists.