Here are some good sources for simple to advanced instructions and articles in origami.
this is a good source for instructions as well as a guide to paper, books, and origami techniques.
this website also has a youtube channel, and here you can find many well explained instructions for simple to complex origami models.
Robert J Lang has a lot of crease patterns for his models.
this is a website all about origami. there are many diagrams, and there are a lot of pictures.
Origami Tessellations
this is a website all about folding tessalations by Eric Gjerde and has many crease patterns as well as articles.
this website is actualy a huge database for origami. if you are looking for something specific and can't find it easily, you can search this site and find where published instructions for the specific models are available. it also has lots of diagrams.
Beth Johnson Origami
Beth johnson's website has many pictures of her designs as well as instructions for some of them.
These are YouTube channels with good origami instructions.
JM's origami tutorials has instructions for quiet easy models as well as extremely complex ones. some of these model's tutorials can’t be found anywhere else.
This channel has very well explained instructions for intermediate leveled models.
origami with jo nakashima has clear video tutorials for a Ton of beautiful models. there is also a diagram in the corner making it even more easy to understand.
This channel has tutorials for quiet complex models as well as simple ones. the videos are very clear.