Max Popenker's website lists almost all the ones I know of. They are:
Heckler & Koch CAWS (never went into commercial production)
http://world.guns.ru/shotgun/sh18-e.htm
Valtro PM-5
http://world.guns.ru/shotgun/sh25-e.htm
Franchi SPAS-15
http://world.guns.ru/shotgun/sh06-e.htm
Saiga
http://world.guns.ru/shotgun/sh07-e.htm
MAG-7
http://world.guns.ru/shotgun/sh20-e.htm
Atchisson AA-12, and the USAS-12 which is based on it
http://world.guns.ru/shotgun/sh29-e.htm
http://world.guns.ru/shotgun/sh16-e.htm
XM-26LSS (which appears to be able to use Saiga magazines)
http://world.guns.ru/shotgun/sh28-e.htm
Mossberg, who has made a variety of bolt action shotguns over the years, made one that uses a detachable box magazine, the model 695 (there may be other Mossberg bolt-action shotguns that used detachable box magazines, the 695 is just the only one I know of offhand). Mossberg doesn't currently list the 695 on their website, so I guess the 695 is out of production.
Another shotgun that sort of qualifies is the Jackhammer (like the CAWS, it never went into commercial production).
http://world.guns.ru/shotgun/sh10-e.htm
It is essentially a giant gas operated revolver. It is reloaded by removing its cylinder and replacing it with a loaded one (or of course just reloading the empty cylinder), sort of like the Korth revolver. While not a magazine, on the Jackhammer the cylinder does act as a detachable ammunition feeding device.
Detachable box magazine designs have never been, and problably never will be, as popular in shotguns as they are in rifles and handguns. Shotgun ammunition is so much bulkier than pistol and rifle ammunition that the key advantage of box magazines, that they usually provide a significant increase in ammunition capacity, is not realized unless the magazine is very large (like the AA-12's 20 round drum), which ends up making the shotgun bulkier than most users care for. Though the other advanatage of detachable box magazines, a faster reloading time, still remains.