Back in the BBS days, I used to "collect" BBS file transfer protocols. I shared the source code for some of them on GitHub:
* JMODEM: https://github.com/cpeterso/jmodem
* SEAlink (System Enhancement Associates): https://github.com/cpeterso/sealink
* WXMODEM (Windows XMODEM): https://github.com/cpeterso/wxmodem
* ZMax: https://github.com/cpeterso/zmax
I also remember "Leech Modem", a file transfer protocol that was compatible with XMODEM and YMODEM but designed to bypass a BBS's download quotas. The protocol would NAK the last packet and then abort the file transfer. The user had successfully downloaded the file, but the BBS would mistakenly not count the aborted file transfer against the user's download quota.