Let's keep this just to an archive of links, and open a thread for any discussions of them.
First up:
Dunnigan's Complete Wargames Handbook
http://www.professionalwargaming.co.uk/Complete-Wargames-Handbook-Dunnigan.pdf
John Cooper's wargame art page, with downloadable map textures and WWII NATO-icon counter templates for Adobe Illustrator (this things are AWESOME)
Samples: http://www.jrcooper.com/wargameart.htm
Downloads here: http://www.jrcooper.com/gaming.htm
Playtest counters template: http://www.jrcooper.com/playtest.htm
SPI Ancients icons: http://www.jrcooper.com/spilib.htm
Terrain tiles: http://www.jrcooper.com/gaming.htm#terrain_tiles