Owen has posted some great links on the study of pre-modern Korean history. In one of his postings he mentioned the National History Compilation Committee (국사편찬위원회 國史編纂委員會). I poked around the site when Owen linked to it but had no idea they had great modern materials as well.
A Japanese friend of mine just returned to Japan and Waseda after spending a week here collection some colonial period materials. He was hoping he could buy a copy of Yun Ch’i-ho’s original Chinese/English diary while he was here which he had heard was out of print and only now available in Korean. I went used book shopping with him but we had no luck. However, after his return, he discovered—and was kind enough to tell me—that the entire diary is online via the 국사편찬위원회 website.
To find this diary, simply go to the history.go.kr website, enter 尹致昊日記 or 윤치호일기 in the search box and you will find three hits. The first hit will lead you to a volume index, followed by a year and month index where you can read his entries directly online. Whoever compiled it was also nice enough to mark proper nouns as “People” or “Places.” If you are not sure what kind of thing one of the specially colored words are, simply hover your mouse over it and it will tell you whether it is a person, place, etc.