ozean,
I can recommend the Farallon 10BaseT PCMCIA card which is a very good product. Any other vendor that has been in the Mac market for some time (like Asante) will also be a good choice, from them you will get good software instead of just kind of software.
Not all PC ethernet cards work in a Mac, so make sure to choose one that does, and this is basically a matter of software.
Walter.