I have 237GB of data on a 360GB bios rake raid0 on an ntfs filesystem using dmraid. I would like to have this on a reasonable filesystem, without dmraid, i.e. maybe software raid ext3. If you were in this situation (which sucks) how would you move/backup the data most safely and efficiently?

Go borrow a 320GB external hard drive from a friend/foe and transfer the data to it and rebuild. Better yet, go buy one, they're pretty cheap nowadays, I just bought a 500GB Seagate FreeAgent for $200.00 (I know, I got ripped off, but us Canadians have to pay tax on the tax we pay you know). Because you're going to cry hard some day when disaster strikes and you don't have it backed up. I repair computers, I have seen the faces of those who could not take the time or spend the money, first the jaw drops when they here the inevitable bad news, then you see anger in the eyes because you (the repair person) did not perform a holy miracle, then you're (the repair person) hated for a long time.

EDIT: I also do data recovery on drives that still turn, but you're much better off planning ahead and buying an external, it could be as much as 10-25 times cheaper.