Talk to me in Korean is a very good foundation to get started in Korean. It's curriculum is fun to follow and involves a ton of listening. Recommended for Novice - Intermediate levels!
How to Study Korean curriculum is very in depth. They have a lot of grammar points, with a lot of extra vocab to each lesson. Recommended for all levels.
Stemming from our own server, Study with Bee!'s grammar section is written by a learner of the Korean language and very intuitive! Recommended for all levels.
(also check out the rest of her website)