I was only familiar with three of them: Hampsterdance (which I discovered much later than 1998), Dancing Baby, and Jib-Jab (and I only know about Jib-Jab because some of their cartoon parodies have been featured on the Tonight Show).
geez, the only one I don't know is #7 (Ellen Feiss). I probably need to get off-line more...
Im shocked that all your base isn't number one. never heard of the Mahir one.