Six years ago when I published parts of this bibliography for the first time, the best online bibliography concerning the Korean history compiled by Ken Robinson was still in its infancy, as was The Harvard Korean Studies Bibliography.
Now, six years later both projects seem to be finished. The Korean History Bibliography contains a chapter Religion and Philosophy : Confucianism, in which you can find more general literature concerning Korean philosophy, but be cautious, some of the titles listed in English are only available in Korean. The Harvard Korean Studies Bibliography contains now more than 80,000 references on Korea, but is only available on CD. The majority of these references are Enlglish language works. According to the system requirements, the users unfortunately need a Macintosh or Windows machine. [ Tip for Linux users : install VMware which enables you to run Windows (95,98,NT) as guest operating system.]

If you are just looking for a good starting point, I would like to recommend the following two books :

• Sourcebook of Korean Civilization, Vol.1, Edited by Peter H. Lee features three periods of Korean history: the Three Kingdoms and Unified Silla (57 B.C.?), Koryo (918?), and Early Choson (1392-1600).
• Sourcebook of Korean Civilization, Vol.2, Edited by Peter H. Lee covers the seventeenth century to the modern period -- Late Choson (1600-1860) and Modern /1860-1945).