Setting up NFS exports under Leopard is insanely easy: just add an entry to (or more usually, create) /etc/exports, and it gets picked up automatically. This file survives reboots, as well; pretty cool.
Here's an example:
muse:~ root# cat /etc/exports
/Volumes/BigDisk/Panic -maproot=netroot 10.0.1.1
muse:~ root# showmount -e
Exports list on localhost:
/Volumes/BigDisk/Panic 10.0.1.1
muse:~ root#
[robg adds: I haven't tested this one.]

