i tried the "Wintech USB 2.0 LanCard Model: LAU-15 (CK0049C) successful. They are working with the mcs7830 driver.
I dont know if the (unmodified) RPi can provide enough power. On my RPi i shortened both USB-fuses and use an unfused separate power supply/input (5V 1,5A).
Just bought a Pluscom usb to ethernet adapter off ebay (item id: 220708690400). Plugged it in and red light is on. Ifconfig shows eth1 and eth0 in the terminal window. But no data being transmitted (dont know if this info helps but shows status '....RUNNING MULTICAST...'). How can I trouble shoot this? Do I need a specific driver using apt-get?