On the old 6200-series you could change the stack-ports to ethernet and then use them as 10Gbit regular ethernet connections (granted it was using non-standard physical plugs/ports/cables). I used this feature extensively in iSCSI SAN setups to allow upgrading switch firmwares 1 at a time instead of needing the full downtime to reboot the whole stack in 1 go.
Does anyone know if the N2k and/or N3k do this as well with their stacking ports?