http://hanbooks.com/ but I think ultimately it's more expensive than YA (but hey, Korean books \o/). International shipping fees are killers, imho.

http://www.dvdasian.com/ Lots of dvds.

Only for MBC's dramas http://www.mbcdvd.com

Iirc when City Hall could only be pre-ordered from http://shop.innolife.com at the beginning and many people bought it from there. It's a Chinese site. From what I was told it was reliable and very popular, but I can't vouch for it since I've never bought anything from there. Should you need assistance in buying dvds and/or opening accounts, Im sure I can find the link with the tutorial that was posted at soompi.

And I don't know if Kyobo ships overseas, but I'm fairly sure they sell dvds and cds