Here is a running list of all the stuff I'm putting on the site's FTP for public consumption.

Huge thanks to x-M-x for graciously allowing me to post this content on AVP UNKNOWN.

Tools
AVP Editing Tools, pretty much everything you ever need to do editing work in AVP Gold Edition: http://avpunknown.com/avpclassic/files/tools/avpeditingtools.zip
AVP Gold Source Code: http://avpunknown.com/avpclassic/files/tools/AvP_Source-Version-116c.zip

Mods
Cancer Black (total conversion mod for AVP Gold Edition): http://avpunknown.com/avpclassic/files/mods/cancer_black.zip
Melpyth (mod for AVP Gold Edition): http://avpunknown.com/avpclassic/files/mods/melpyth.zip
uMod (mod for AvP Classic 2000): http://avpunknown.com/avpclassic/files/mods/umod.zip

Map Pack
Universal Map Pack 1.5.5 (complete files): http://avpunknown.com/avpclassic/files/maps/universal_map_pack.zip

Misc. Maps/Packs
Shotgun Level Pack (adds shotgun to SP for the MelPyth mod): http://avpunknown.com/avpclassic/files/maps/shotgun_level_pack.zip
Weapon Continuity Pack (adds previous level's weapons to beginning of new marine level): http://avpunknown.com/avpclassic/files/maps/weapon_continuity_pack.zip
Flight Pack: http://avpunknown.com/avpclassic/files/maps/flight_pack.zip

Skins
Universal Skins Pack: http://avpunknown.com/avpclassic/files/skins/universal_skins_pack.zip
Custom Menu Backgrounds: http://avpunknown.com/avpclassic/files/skins/custom_menu_backgrounds.zip
New Single-Player Icons: http://avpunknown.com/avpclassic/files/skins/new_level_icons.zip

Sounds
Universal Sounds Pack: http://avpunknown.com/avpclassic/files/sounds/universal_sounds_pack.zip

Strategy Guide
http://avpunknown.com/avpclassic/files/avp_strategy_guide.zip