I use D-Link DFE-530TX+ cards (they use a Realtek 8139D), Genesis (bundled with OS 3.9--doesn't support DHCP, but it works) and Cloanto's Amiga Explorer for PC <-> Amiga file transfers. All are very simple to set up, but you won't get a lot of features. For example, all transfers via Amiga Explorer are initiated on the PC side, but it's very useful for emulation enthusiasts. Of course, Genesis provides a relatively complete IP stack, so you can run whatever software you want. (You didn't mention PCs in your question, but they usually come up sooner or later.)
The Realtek 8139x cards are universally supported (Titan's latest OpenPCI driver works well), so if you have multiple Amiga setups (e.g. A1200 w/ Mediator, A3000 w/ Prometheus, Amithlon, etc.), you can standardize your software configuration.
Trev