It is almost impossible to have an ethernet board for an A500, unless you have a zorro2 expander.
But, i think a [color=ff0000]serial bluetooth adaptater[/color][/b][/u] could make it. In the past, i used to have a nullmodem cable with tcp/ip working on my A1200 to share internet access. Bluetooth serial adaptater can do pretty much the same, probably faster and equivalent to an amiga ethernet board (that are not usually as fast as on PC).
I am amazed that, although WiFi is used by several amigans on A600 or A1200 with PCMCIA adaptater, no one care about bluetooth on amiga.