I have an Asus® K8N-E Deluxe with nForce™3-250GB chipset.
The chipset has a built-in Gigabit MAC with external Marvell PHY It supports - 10/100/1000 BASE-T Ethernet

Nvidia has recent Linux drivers:
http://www.nvidia.com/object/linux_nforce_1.0-0283

Havent tried getting them working with Knoppix yet though.

I will dump the CD to a Read/Write medium (harddrive or USB key) and see if the drivers will install. I want to try getting Knoppix running on a USB key anyway. I only have a 128MB key currently... might need to upgrade