Many universities have Korean language programs for international learners and often break up their classes into full-time and part-time options. The most popular programs in Seoul include Yonsei University, which is the oldest program, has a variety of classes and textbooks, and is very grammar focused; Sogang University, which is popular among expats as their program is very practical for living in Korea; and Seoul National University, whose textbooks are used by a number of other universities and language schools. Language classes in universities roughly cost the same in tuition but the quality and the usability of the contents varies. Doing an online search of the program and their textbooks will help you choose the right program.
One of the difficulties is most students stop after completing level 1, which leads programs with smaller numbers of students unable to host classes from level 2 or 3. If you have a choice of universities, find out how many classes they have for each level either currently or last semester as they don't know exactly how many classes they'll have for the upcoming semester until right before classes start.
If formal self-study is more fitting for you, check out the textbooks mentioned above. If you want to focus on grammar, a popular series is Korean Grammar in Use by Darakwon (다락원). There are three levels and corresponding workbooks are also available. Yonsei University’s Korean Grammar for International Learners is a popular book available in several languages and with an optional workbook. If you are more visual and want to learn some of the words for the objects you see around you in Korea, Darakwon has two versions of Korean Picture Dictionary; the English, Japanese, and Chinese edition; and the Vietnamese, Indonesian, and Mongolian edition. An app of the first version is available by Daolsoft.
Various cities have also setup their own resources centers for international residents and frequently have free or subsidized Korean language classes. This includes the Seoul Global Center, Daejeon International Center, and Busan Global Center. An internet search will help you know what is available in your area.
While historically there have not been many textbook options to choose from, online programs have been filling the void and offering a variety of options and formats. Podcasts, YouTube channels, and dedicated websites have popped up and some have disappeared. The following list should be considered incomplete as new sites and videos will open and some websites will close. Like everything else on this site, please let us know if there are resources you think would be beneficial to the international community and we'll add them here.
Talk to Me in Korean (TTMIK) - Mixture of paid and free content. Books, e-books, audio courses, and video courses. Requires an ID through Google or Facebook to access content.
Korean Wiki Project - As people contribute to the site, the contents are expanded. Vocab, grammar, TTMIK lessons, and Kpop lyric breakdown.
Sogang Korean Program - The same Sogang University mentioned above has an online version of some of their curriculum. Older website and only runs with Flash plugins and requires use of Internet Explorer; the main browser used in Korea.
Learn Korean LP - Grammar courses, word lists, audio recordings. Appears to no longer be updated but audio/video content works.
GoBillyKorean - A Westerner in Korea who learned the language online and wants to help others achieve what he has. New videos weekly and many playlists are free, his bilingual book is his only paid content.
seemile Korean 씨마일 한국어 - Multiple teachers with a number of videos grouped in playlists for English speakers, Vietnamese, Japanese, and Chinese. Their SEEMILE English channel uses English for teaching English and their SEEMILE Chinese - 씨마일 중국어 channel uses English to teach Chinese.
Memrise - Website and iOS and Android app with user-created flashcard content. Multiple flashcard sets exist for Korean Immigration and Integration Program classes. Free but with paid options.
Anki - Free and open-source software for spaced repetition flashcards. User-created content is available or create your own. Windows, Mac, Linux, iOS, Android.
HelloTalk - Android and iOS-based chat app with the purpose of talking online with language partners in spoken or written form.
Daum - Domestic search engine's multilingual dictionary. Android app is available.
Naver - Domestic search engine's multilingual dictionary. Android app is available. Harder to use the website version if you have trouble reading Korean.
Naver - Domestically most popular online translation program. Android and iOS versions available.
Kakao (Daum) - Translation site is under development with a beta version currently available.
Google - Google's search engine's multilingual dictionary. Apps are available for Android and iOS.