I have just borrowed a Dlink DFE-580TX quad ethernet card from the office where we are expermienting with them. We have now tested them on both 2.4.x and 2.2.19 kernels and they work a treat. You can run the four ports independently or as one extra wide-band channel.

The driver modules you need are pci-scan.o and sundance.o. The latest versions can be downloaded from www.scyld.com