My experience is similar to a few people who have commented already. AMVs through webrings and mailing lists, with some vids included on dubbed tapes, mass consumption and exposure at anime conventions when 56k dialup was the fastest thing around.

I can't remember specific vids, though I can remember seeing early ones in Ranma 1/2 and Tenchi Muyo fandoms. I also remember a Golden Boy video that was specifically not the one by Kevin Caldwell, but my google is failing me.

I remember a lot of early 2000s anime music videos did lip syncing for comedic effect, then it seemed for a long time to just be good timing and narrative, and then around mid-2000s the lip-syncing trend came back, but maybe that's just the fandoms I was exposed to!