To get a grip of the compatible PCMCIA ethernet cards check the compatibility list in cnet archive. While you're in aminet, get these 3 packs:
CardPatch.lha
CardReset.lha
cnetdevice.lha
The first 2 are for the PCMCIA bugs. Both needed.
The later one is the device needed for using the PCMCIA ethernet card. It is compatible with a variety of cards. You can check the list as i told to see what is supported and what not. I myself use them 3 and a Zoom X4 ADSL router modem, works flawless! :-D