Hi Dylan,
there is a lot more.. you can check out all friction classes in src/m/classes:
friction.m
frictioncoulomb.m
frictioncoulomb2.m
frictionhydro.m
frictionjosh.m
frictionpism.m
frictionschoof.m
frictionshakti.m
frictiontemp.m
frictiontsai.m
frictionwaterlayer.m
frictionweertman.m
frictionweertmantemp.m
I hope this helps
Mathieu