My ISP upgraded my internet connection speed to a whopping 120 Mbit. I am using a mac mini as my internet router. As you may be aware, the mini has only one network interface, so I added a second interface using a USB to ethernet adapter. This adapter was limited to 100 Mbit, so to make full use of the 120 Mbit connection, I had to upgrade this adapter.
I took the gamble and bought the Belkin Gigabit USB 2.0 adapter. I could not figure out if it would work with Linux, but on the box it officially supports Mac OS X, which is always a good sign.
This adapter is recognized by Debian Linux without a hitch:
Mini:~# ethtool -i eth0 driver: asix version: 14-Jun-2006 firmware-version: ASIX AX88178 USB 2.0 Ethernet bus-info: usb-0000:00:1d.7-5
Bus 005 Device 004: ID 050d:5055 Belkin Components F5D5055 Gigabit Network Adapter [AX88xxx]
I did not test the actuall performance of this adapter, but it at least goes beyond the 100 Mbit (it does 120 Mbit at least). I expect it to be limited at say max 300 Mbit, being constrained by the maximum speed of USB 2.0.