Ok, here's my hard-earned experience with usb ethernet adapters with the ia1:
I first bought the linksys usb100m. It is very compact and looked promising. But it did *not* work. I even tried the latest redhat 7.2 with my laptop. From my research, I believe it has something new and is not a standard chipset.
Next, I tried a Netgear ea-101c. It was $19 refurbished, but it worked poorly. It would go offline after a while with lots of console messages. A little research on http://www.linux-usb.org showed that it could just be crappy hardware.
Then I finally followed a link on the slashdot discussion and found this tiny gem:
It's a compex eu202 usb ethernet adapter.
There was no indication that it would work, but I took a chance and ordered one for $16. I was pleasantly surprised to find out it uses the pegasus II chipset and works just fine.
Hope this helps