The Sager 9880 does offer RAID 0 between two internal drives. Though after seeing one of these beasts in person, they definitly aren't laptops, but instead portable computers in the true sense.

I can't remember who it was, but someone used to offer a "desktop replacement" notebook that used both 3.5 ich drives, and desktop sized memory. I want to say it was either Asus or Acer, but I can't find it now.