what do you need it for ? you need a lot of other stuff to make an ethernet port.
either go for a ethernet module (including coupling transformer, the PHY chip and eventually with MAC as well) or just solder a RJ45 to a piece of protoboard if you have the rest of the circuitry elsewhere.
if you're thinking about "bit-banging" ethernet, then you will need a hell-of-a-fast processor or FPGA for that.
the best way is to buy a ready-to-go ethernet module - search on dealextreme or e-bay.