I love slit-scan effects, it's such a simple but powerful concept.

They're actually really easy to do now in post, After Effects has an effect called time displacement that allows you to displace time on a per pixel level. So to recreate a standard slit scan you'd just supply it with a gradient from black to white, but you can also create even more bizarre effects by mapping the pixels differently.

A few months ago I did all the effects for some music videos, and I created multiple effects based on slit-screen. Things like, having the video smoothly break apart into slices where the time moves at different speeds and then smoothly splice itself back together.

Another cool effect I figured out: using a blurred copy of the video as the time displacement mapping. This makes everything that's colored similarly move together in time, but out of sync with everything else.

I did that effect for a video that was just one long shot, and then I rotoscoped out the performers so they move in regular time and match the music: https://youtu.be/-0zO7Fnqnvs

I really love old school effects work, they're a constant source of inspiration.