starlady

Cutting out a frame from clip A and inserting clip B into it, or overlaying clip B onto clip A in some way. Examples: The Test by heresluck, which overlays Star Trek TOS onto footage from the Reboot movie to show us stuff about the Kirk/Spock relationship, and I'm your man by charmax which does it with mirrors.

Sometimes people cut the screen into sections and show different things in each section, sort of like the opening credits sequence to every 70s TV show ever ;) I'm not thinking any really good examples though. Oh! Yes! Vogue by luminosity has a lot of this, though there's a lot of other stuff going on there too.

Something else I've seen is people using effects to texturise (for want of a better word) footage, to make it look old or something. You quite often see sepia tones, old film effects, and similar. Examples: Closer by T. Jonesy and Killa, go back to sleep, by TikiTyler9 (also does other stuff with colour and black and white), I am/Lamb by lim.

lim has a number of vids that have a sketchy, hand-drawn sort of a texture; "Us" is the best known of them, but "This is how it works" also does this. Some of her vids have a different, scrapbooky sort of effect, see eg. "Wallpaper" and "People are People".

(Wow, I wish some of these vidders would write (or point me at) tutorials on how to do this stuff in Final Cut.)