The Jeju Studies Archive run by the 제주학연구센터 has a wealth of freely accessible articles on the dialect of Jeju, which many argue can be classified as a separate language altogether.
The Jeju Dialect Institute – 제주어연구소 – is a good resource for research, news and information about Jeju Islanders’ unique way of speaking.
The 제주어보전회 website has some Korean-language information on Jeju-eo: the Jeju language.
Modern and Classical Korean
The 국사편찬위원회 National Institute of Korean History has an online Korean-English dictionary of historical terms.
The 한국학중앙연구원 Academy of Korean Studies has a useful 한국학 용어/용례 사전 : Korean-English dictionary of terminology.
Hanja : Chinese Characters
The Korean Genealogy website has a great list of hanja, a comprehensive list of Korean family surnames, clans and branches, a chart of all the terms of years used for the reigns of kings, and all the terms of years correlated to different calendar systems.
The Korean Hanja App website is an excellent resource for reading texts written in classical Korean using Chinese characters. There are no limits to the length of text you can enter, the results are displayed in a crisp, clear format, and definitions are given in both Korean and English.
Zonmal is a very useful online resource for studying hanja. You can search by radical, number of strokes, shape, sound, meaning or national examination level, and it offers example words for each character.
오픈마인드인포테인먼트 Open Mind Infotainment has a great dictionary, especially for its explanations of radicals and word lists.
The 전통문화연구회 Institute of Traditional Culture has an awesome online tool that adds hanja to any text, and inserts hanja next to the original Korean in any website.
MDGB has a very useful tool that allows you to enter any Chinese text and get a list of the pinyin pronunciations and all meanings of the characters or words. The layout is very easy to read and is made available in a printable format.
Chinese-Tools has a useful Chinese annotation tool that shows younthe pinyin and definitions for any text in a clean, easy to read format.