Save/ROM dumper

Use either the GB ROM, or the GBA ROM with a compatible flashcart to prepare dumping GB/GBC saves and ROMs through the link cable.
The python script will read the data off of an USB to Game Boy Link Cable Adapter's interface.
You can then decide how to save it.

It's EXTREMELY slow! It's not recommended to dump ROMs unless it's absolutely needed.
Dumping saves (SRAM) will take up to 30 minutes depending on the game (Pokémon Gold required about 10 minutes, from the tests I ran).

If things don't work properly on Windows, check libusb.