(I'm surprised noone responded to this one yet)

For the NAS, I'd recommend ext4. ReadyNAS is making the switch with their products, mostly to avoid the limits of ext3. With 4k block sizes, an ext3 volume is limited to 16TB. Your home NAS probably won't have that capacity quite yet, but there are a number of other benefits that come with ext4, and it's been marked production ready by enough people that I trust it now.

The Wikipedia article on ext4 does a good job of showing what is new for ext4.