I think there already is a topic 'bout this but anyway:
Youtube channels:
Sara Adams(happyfolding.com)
Jo Nakashima
Tadashi Mori
Evan Zodl(EZorigami)
Alexander Kurth(quiet marverick)
Anna Kastlunger(Origami8)
All of them have very cool instructional videos, timelapses, videos of hard steps on a complex model and giveaways.
Some sites:
Passion Origami (Nicolas Terry) Some diagrams and CPs and a lot of pictures of models.
Happyfolding (Sara Adams) Some diagrams, instructional videos, a dictionary, paper reviews and a list of Books that are worth buying.
Neorigami (Gerardo) A lot of cool Articles and Diagrams. Also the home of the MINI NEO magazine.
Gilad Origami (Gilad Aharoni) Best site of Book reviews. This is the site to visit before buying a book. Also a pretty big gallery, diagrams to some simple models and interesting articles, a guy
ide to wetfolding, how to obtain paper shapes and divisions and an almost complete list of Japanese Designers.
Meenakshi MukerjiA lot of diagrams for her and other modulars and links to single sheet diagrams.
Origami Yard (Tadashi Mori)A huge gallery with many complex models, some instructional videos, diagrams and CPs.
Lang Origami (Robert J. Lang)Has a lot of pictures and CPs of Lang's models, some paper reviews and articles.
Shops:
Mulberry Paper and moreSome cool handmade papers.
Paper Jade I don't know a lot about this because I haven't ordered from them but I see that they have some Kami, Tant, EH and others.
Kims Crane Like I said above, I don't know because I haven't ordered.
Origami Paper Monster They only ship To USA and Canada but have a lot of cool papers and they even sell MC.
Modulor Based in Germany, but they ship worldwide, this shop sells a lot of sorts of Kraft, Elephant Hyde, Stardream, Efalin, handmade papers and if you search a bit you'll even find MC.
Origami-shop Based in France, but they ship worldwide. This shop sells almost any paper. From kraft and Tant to the more unknown Rhino, Lizard and Bear Hyde.
BOS Supplies Some paper,books and a lot of BOS booklets.
OUSA Source Sells many books and papers, and if you're a member you'll get a discount on every item.
Amazon You'll find a lot of books and papers if you search for origami on amazon.
BOS British Origami Society. Has some diagrams, articles, comics and jokes. Here you can join the BOS and if you're a member attend their Spring and Autumn Conventions.
OUSA Origami USA. Has some diagrams (both for free and paid). If you're a member you can read the online magazine the Fold, buy from the Source with discount on every article and attend their conventions.