@williamatics For Houdini specifically it’s hard to find free courses. According to SideFX you have a 10 day free trial on Pluralsight, maybe you can get some good start there:
https://www.sidefx.com/education/training-centers/
Otherwise the first result of “houdini courses youtube” search sent me on Surfaced Studio channel:
https://www.youtube.com/watch?v=pu_i6jeayLA
What other software did you have in mind ?