This isn't exactly zentangle related, but I came across this cool site, Doodletuts, lured by the prospect of a giveaway (yeah! They have a giveaway going now for some Letraset promarkers!).
Doodletuts describes themselves as: "a blog/art community designed to deliver some of the best tutorials on drawing, sketching and art techniques on the web. Doodletuts aims to deliver tutorials for real beginners right through to articles aimed at the more advanced readers.
Our main aim is to keep all of our tutorials easy to follow and in a understandable format so that anyone of any level can follow them."
From what I've seen they are heavy on Manga technique, but, hey!, it might be interesting to try doing a zentangle with Manga influence. I'm putting that on my things to do list (which is wa-a-a-ay too long already, lol).
The Archive section is nicely laid out giving you more than one way to browse through past postings. I checked out some of the reviews and added a few things to my Want to Have list (another one of those long, long growing things!). Most of the brands reviewed are British/European, which makes some of them hard to find for my North American self. I like that. I can learn about brands that I might be unaware of otherwise, and keep my eye peeled for a chance to find them.
So, even if you aren't into Manga, I think this is a cool site, and worth checking out for the reviews and giveaways, alone. I intend to browse through the tutorials as well. You never know what technique might start a creative avalanche!