Fred Fish collected and published a great collection of public domain, freeware and shareware Amiga software between 1986 and 1994. He made over 1000 disks. It's one of the best resources for older Amigas, like the A500, as most of these programs cannot be found on Aminet or elsewhere. This is the full catalog of the disks, to help with finding what you're looking for.
The contents of the disks can be downloaded from ftp.funet.fi (in lha format) or the Internet archive.
Contents of the disks (Disk Number: Program | Description), Cross Reference (Program | Version | Disk Number | Author, in alphabetical order), if you're after a particular software, you can see which disk contains it.