Similar to foleyjo, I used to:
Get the adf of the net with my PC, copy those each one to a PC floppy (1.4Mb), on the Amiga side I was lucky enough to have a High Density external floppy drive and cross-dos (the Amiga's PC floppy reading software).
So now I have the adf file on the Amiga's harddrive, I used ADF2Disk to convert the image back onto a real Amiga floppy.
To do all this you need:
-An Amiga with a harddrive!
-A high density floppy drive
-Some old blank Amigha disks
-Patience.
Nowdays, I just use WinUAE, its a lot easier.
But if your determined, You might be able to get those adfs onto your A600 using a PCMCIA - Compact Flash adapter in the A600 slot?
Write adf's to the CF card on PC, insert the PCMCIA-CF card into the A600 and convert the files using ADF2Disk (see Aminet).
I dont know if this will work, I never got it to work on my A1200 but it coulve been the PCMCIA-CF adapter I had was incompatable with the Amiga, I started using WinUAE and never botherd to solve it.