USA
www.gamingetc.com <--- smooth orders, no problems
www.strikezoneonline.com <--- ordered once, things went fine
www.trollandtoad.com <--- have had poorly packaged stuff more than once, and cards in conditions below what's graded, starting to get turned off
www.dacardworld.com <--- several orders for sealed product, prompt and smooth
www.funkyfruitstand.com <--- this guy is awesomeness
www.cardhaus.com <--- only ordered from twice, both good experiences
www.starcitygames.com <--- many orders, no problems
www.mtgmintcard.com <--- not sure why this is under the USA tab, I've ordered stuff from them a few times from their website or on ebay (as goods-seller), item locations are stated to be Seattle Washington, however ebay member location is Hong Kong, and everything I've ever ordered from them has been posted from Hong Kong. Always get good cards, but if you're ordering expecting it to arrive quick as you "think" it ships from the US, you'll be waiting longer than expected (~2 weeks).
www.manaleak.com <--- based out of UK? Why under US tab?
www.coolstuffinc.com <--- have fairly decent pricing on some things (like NM alt 4th set for $399, that I should've bought when I first spied it)
www.gatheringground.com <--- bait & switch pricing tactics, completely rude customer service, shadiness on a stick!
ITALY
www.magicmarket.it <--- site has moved to
http://www.mm25.it, could not find any singles anywhere, not sure if they carry them at all
http://www.magickingdom.it/public/catalog/ <--- link is dead, possibly store too, which is sad as I've ordered from them in the past and had no problems, used to be a good source of ITL foils
http://www.magic-store.it/ <--- site active but have yet to get any sort of response to my emails
http://www.magorosso.it/ <--- site active but have yet to get any sort of response to my emails
PORTUGAL
http://www.magictuga.com <--- site active but have yet to get any sort of response to my emails
http://mtgdraw.com <--- link is dead
GERMANY
www.trader-online.de <--- placed two large orders, ordering process and communication were good, just awaiting card arrivals
FRANCE
www.magicbazar.fr <--- placed one large order, communication good and cards shipped fast
SPAIN
www.magicevolution.com <--- site is nice and easy to navigate, but I couldn't figure out how to register for an account so that I could order cards, so I just dealt directly with David.