Apart from Marble Hornets, I've only watched 2 episodes of EverymanHYBRID and read about half of Just Another Fool. How good are these other series? Same question for the blogs; I don't find them quite as entertaining, though.
The only blogs I'd recommend, aside from the meta blogs (e.g. Compile Truth, Slenderbloggins), are M's
Tutorial (extremely influential on later blogs and the mythos in general) and
Seeking Truth/
The Mystic (great story). I've read a few others, but they haven't been as interesting. The meta blog summaries adequately cover them IMO. I actually haven't read any of the other well-known ones (like Maduin's, Zero's, Ava's, Reach's, and so forth), so I can't comment on those.
As for video series,
Tribe Twelve has great effects but takes a while to really get going. The acting remains sub-par, but at least it
has acting, unlike most of Marble Hornets.
Angel's Game is supposed to be pretty good, but I haven't watched it. There are several YouTube accounts involved, but the one I linked should have a playlist that includes
everything in chronological order. That's pretty much all I can say on the video front. I know there are more out there, but I can't say much about them.
Almost forgot to add links to meta blogs:
Compile Truth (jumped the shark recently, but the various summary videos are nice),
Slenderbloggins,
Golom Tulpa Anima (hasn't updated in ages),
The Slendy Review (likewise),
Encyclopedia Slenderia (sporadic updates).