GunBroker.com - pistols, shotguns, rifles, collectible, hunting, etc.
http://www.gunbroker.com/

Auction Arms - antique guns, collectible, and more
http://www.auctionarms.com/

Wards Auctions - mostly collectibles, also fishing and decoys
https://www.wardscollectibles.com/

eGun Auctions
http://www.e-gun.net/cgi-bin/ua/main.pl

Antique Guns Auctions
http://www.antiqueguns.com/auction/html/categories.htm

The #1 UK Online Auction for shooting Enthusiasts.
http://www.gundeals.co.uk/

Gun Lodge.com
http://gun-lodge.com/cgi-bin/Auction

Gunslive.com
http://www.gunslive.com/

Field and Clays Auctions - shotguns, trapguns, skeet, hunting
http://www.fieldandclays.com/auctions.htm

Guns and All Firearms Auction
http://gunsandall.com/

eBang.com
http://www.ebang.com/

The Knife Auction
http://www.theknifeauction.com/

A-Gun.com...also knives
http://www.a-gun.com/

Gunhouse.com
http://www.gunhouse.com/

Bluebroker.com
http://www.bluebroker.com/

Gun Monster
http://www.gunmonster.com/

Buy Sell Guns Online Auction
http://www.buysellguns.com/

Mountain Morning Gun Auctions
http://mountainmorningauctionsandclassifieds.com/

Sports Trading.com
http://www.sports-trading.com/

I Sold My Gun.com
http://www.isoldmygun.com/

Gunrunner Auctions
http://www.gunrunnerauctions.com/index.cfm

Hunterbid.com...gunstock blanks
http://www.hunterbid.com/

Rock Island Auction Company - high quality antique gun auction house
http://www.rockislandauction.com/