Even when you have finished installing NetBSD/amiga, there are several post-installation steps if you want to enjoy your new operating system. These are some small notes of information I gathered that makes the system way more friendly. Many thanks to Karl Jeacle for his post about NetBSD/amiga and the people at the NetBSD/amiga mail-list for all the help and question answering.
Supported Amiga hardware in NetBSD can be found here, including ethernet cards. In Amiga 600 or Amiga 1200 it is possible to use PCMCIA cards, however, only those compatible with NE2000 will work. You can find a list of tested ethernet cards here. I can confirm the following PCMCIA ethernet cards works well in both, AmigaOS and NetBSD/amiga: