Back in the day I used
Mocha W32 PPP as a ppp gateway for an old laptop to my Windows XP box to connect to the internet because the laptop lacked an ethernet port, and I was too cheap to get a pcmcia card for it.
It says palm/windows ce but it should work with an Amiga just the same.
Oh and once you have that running (the IP connection to your pc) you could setup SAMBA for sharing files.
