LivingDead.com was without doubt one of the best dead sites out there, with in depth info on all three of Romero's Living Dead Trilogy. However, it seems to have vanished into the valley of death and is seemingly never going to come back...
HomepageOfTheDead.com is another unbelievable dead database. The film information is limited but the site has a massive fiction section and some great message boards.
Dawn of the Dead 2001 is a relatively new site. Richard has done a great job on the site and we should hopefully have some new sections soon!
New Dimensions is up there with the best too. Nick has covered virtually every decent horror flick and has a great section on Romero's trilogy.
A Dead Universe - a very new, but nonetheless great site about the trilogy.
Day of the Dead is Jamie's great tribute to - you guessed it - Day of the Dead.