FYI, I've made some progress on catching up on webcomics. I figure that I'll make these monthly reports, since I didn't get through many this month. This will also be as much for my own reference as anything. Here we go:
The Unspeakable Vault of Doom: I caught up through vault 544. Overall, the comic's OK. It makes more sense as one comic of many that I read, and I think that it's the only comic dedicated to Lovecraftian humor that I had on my list.
The Book of Biff: I caught up through the latest episode, which was some time in 2014. I've moved it from active to hiatused.
xkcd: I caught up through episode 1739: Fixing Problems. This comic has gotten better over the years, or maybe it's just accumulated more gems in its long run.
Little Vampires: I only started catching up on this one. I don't remember exactly where I left off on my previous catch-up, so I started at the beginning of the Welcome to Monsterdell arc.
I'll let you guys know how this goes next month.