The FFXII site is up (or it has for sometime, if so, then its been updated) although, there's not much there.
http://www.ff12.com/
About FFVII:AC, here's a little snip-it on the plot from rpgfan.com:
"At a hotel near Chiba's Makuhari Messe, Square Enix has confirmed that just like Final Fantasy VII back then, Final Fantasy VII: Advent Children is being developed by Yoshinori Kitase's production team 1. Advent Children will be a high-quality CG movie of about 60 minutes in length. Final Fantasy VII's returning protagonist, Cloud Strife, will face a new foe and his calm, post-meteor world [will face] a new threat in form of the Star Scar Syndrome. Plans for this new project were drawn up 1.5 years ago and members from the original Final Fantasy VII development team have been brought together again."