Hanja (한자 - 漢字) are Chinese characters used in Korean. 70% of the Korean vocabulary comes from hanja, though Korea has been using only hangeul since some time in the 1950s and at first glance the language doesn't appear to have been as strongly influenced by Chinese as it has been.
Hanja is a cognate of the word kanji (かんじ-漢字) in Japanese and hanzi (漢字) in Manadrin Chinese. Korean hanja is unsimplified unlike Japanese kanji which were lightly simplified after World War II as well as mainland Chinese hanzi which were simplified later at a later date, though in a different manner and usually with far less strokes.
There appears to have been an attempt in Korea to simplify hanja for a Korean audience, but the method appears to be a haphazard mishmashing of Japanese and Chinese simplification together, and a clear reason is lacking for the change. Hanja textbooks one year ago did not have this simplification, but the books for the 한자검정능력시험 (Hanja proficiency test) seem to have these new simplified characters here and there.
- e-hanja: Free; registration with 주민등록번호 required.
- Naver 한자사전: Free; registration not required.
- 모로미: Free; registration not required.
- 전자한자자전: Free; registration not required.
- 존 한자사전: Free; registration not required.
- Mr. Oh's Hanja page: containing Hanja lessons written in English.
- Basic Hanja: containing Hanja characters, with Hangeul and pronunciation.
- Pictorial Sino-Korean Characters: Fun With Hancha by Jacob Kim
- Learn Hanja: the Fun way by Lee Young Hee
- A Guide to Korean Characters by Bruce K. Grant