A long time ago, http://www.natsemi.com created an Ethernet controller chip called the 8390. Datatsheets are on their website. This chip was copied many times by other vendors. http://www.davicom8.com produces an extremely low cost NE2000 compatible chip called the DM9008. Its priced around $5.10 in 100pcs quantities.
I will be testing primarily with this chip since it is used on MANY brands of ethernet cards.
--PehrAnderson