TFTools:
https://github.com/agranlund/tftools
Atari drivers for getting the most out of the excellent TF53x accelerators on Atari.


Dallas realtime clock drivers:

https://github.com/agranlund/rtc
TOS drivers for DS1216 / DS1315 connected to ROM or cartridge port.


Automatic screenmode switcher for ubeswitch or ET4000:

https://github.com/agranlund/modesw
Allows starting ST-Low color games from a mono desktop if using an ubeswitch, or from an ET4000 desktop.
Lacescan support is experimental but untested.