I've found a lot of intresting games at second hand stores. Goodwill and salvation army stores are good places to check, as is any pawn or thrift shop. If your willing to get into bidding matches, goodwill has a auction website as well. (I've never used it though, since they don't take paypal)
As for dust, for cartridge games it doesn't really matter if they are in a dusty area. Well, except the ds and 3ds carts - Much harder to fit a qtip inside them to clean the contacts. All that you'd really need to worry about is moisture.
Anyway, for my Steam collection see my profile. Way to many to list.
PC - Hard copies w/cases. Have a lot more loose discs on a spindle, somewhere.
Command and Conquer: The First Decade
Rainbow Six 3: Raven Shield
Medal of Honor: Airbourne
Fallout Classics Collection
Fallout 3 GOTY Edition
Star Wars Fan Favorites I Collection (Battlefront I/II, Republic Commando)
Quake 4
Sins of a Solar Empire: Trinity
Supreme Commander Forged Alliance
Halo 2
Battlefield 1942
Battlefield 2 + Special Forces
Star Wars Empire at War Gold Pack
Megaman X5
Heavy Gear
Home World GOTY
Descent: Destination Saturn
Survivor: The Interactive Game
Age of Empires III
Command and Conquer (CnC 95)
Alone in the Dark 2
The Iron Plague
Star Trek 25th Anniversary
PS1
Resident Evil 2
Syphon Filter 2
DS
Fossil Fighters
SMT Devil Survivor
Infinite Space
Yugioh World Championship 08
Yugioh GX Spirit Caller
Legacy of Ys Books I and II
Ragnarok DS
Advance Wars Days of Ruin
Suikoden Tierkreis
Super Robot Taisen OG Saga Endless Frontieer (And soundtrack)
Front Mission
Time Hollow
Advance Wars Duel Strike
Ghost Trick Phantom Detective
Megaman ZX
Speed Racer
Final Fantasy XII Revenant Wings
Desktop Tower Defense
Jackass The Game
Pokemon Ranger Guardian Signs
Lunar Knights
Metroid Prime Hunters
Metroid Prime First Hunt (DS Demo cart)
Star Wars The Clone Wars Republic Heros
Pokemon Pearl
The World Ends With You
Chrono Trigger
Glory of Heracles
Bleach The Blade of Fate
Star Wars Lethal Alliance
Megaman ZX Advent
SMT Devil Survivor 2
Megaman Zero Collection
Pokemon Black
Lifesigns Surgical Unit
Pokemon Mystery Dungeon Blue Rescue Team
Pokemon Mystery Dungeon Explorers of Darkness
Izuna 2
Dragonquest Monsters Joker
Trauma Center Under The Knife 2
Valkyrie Profile Covenant of the Plume
Luminous Arc
Izuna
Radiant Historia
Fossil Fighters Champions
Pokemon Ranger
Castlevania Portait of Ruin
Custom Robo Arena
Starfox Command
GTA Chinatown Wars
Pokemon Diamond
Golden Sun Dark Dawn
3DS
Etrian Odyssey IV Legends of the Titan (Limited edition)
Etrian Odyssey Untold The Millennium Girl (Limited edition)
Pokemon X
Pokemon Mystery Dungeon Gates to Infinity
Shin Megami Tensei IV (Collectors edition)
PSP
Phantasy Star Portable
Phantasy Star Portable 2
Monster Hunter Freedom
Street Unleashed 2
Ghost Recon Advanced Warfighter 2
Tales of the World Radiant Mythology
Metal Gear Acid 2
Star Ocean First Departure
Guilty Gear Judgement
Guilty Gear XX Accent Core Plus
Dante's Inferno
Persona 3 Portable
Gundam Battle Royal
Growlanser Wayfarer of Time
Megaman Maverick Hunter X
Wipeout Pure
Syphon Filter Logans Shadow
Gundam VS Gundam Next Plus
