Night and Dawn has both been remade, Day is beeing remade as we speak. I liked the Dawn remake (haven't seen Night remake) so it'll be interresting to see if the can make the Day remake as good as the Dawn remake. I didn't care much for the original Day, I found it somewhat boring. Nice effects and all, but I didn't like the story.
When Dawn of the Dead was released in Europe, it was slightly reedited by Dario Argento (whose brother Claudio had been a producer on the film), and a new soundtrack was made by Goblin. It was also retitled Zombie: Dawn of the Dead, or Zombie, or Zombi. So many titles...
For your viewing pleasure, I have trailers for both versions. Funny to see what's focused on in the trailers. It's slightly more gore and action in the European one.
Dawn of the Dead, American style: 9,39Mb.
Zombie: Dawn of the Dead, European style: 12,8Mb.
This film also has one of the best taglines ever: When there's no more room in hell, the dead will walk the earth.
Enjoy it before hell becomes full!
Update 13th november: I didn't know about this, but it seems that someone has made a remake of NOTLD in 3D. Check out the official site here, and the trailer here (QT, direct download, 14,7Mb). This version is made without the involvement of Romero, just so you know. Looks pretty cool though.