Century is a set of free wargames rules for playing ancients wargames set in the period 400BC to 150BC.
Melee and Wizard: The Fantasy Trip Mass Combat Rules
Melee and Wizard is a set of rules modifications to allow you to use The Fantasy Trip / Melee / Wizard for mass combat.
Cleaning and Repairing Second Hand Models
Brushthralls has an informative illustrated tutorial on cleaning and repairing old figures.
Pz8 Fantasy Rules
Pz8 Fantasy Rules are a set of two-page free wargames rules for fighting fantasy battles.
Making 15mm Trenches
Itty Bitty Battlefields has a post on making 15mm trench systems on the cheap.