I was about to give up TextMate for this one project because of its lack of Korean input support, but I managed to find a workaround solution. First, download Hetima’s CJK (Chinese/Japanese/Korean) input plugin that emulates smooth typing behavior within TextMate for these Asian languages. Then download the following font types:
http://files.getdropbox.com/u/1370491/TextMate-MalgunGothic.ttf
http://files.getdropbox.com/u/1370491/TextMate-UnDotum.ttf
Phew, I was about to pay $99 for an inferior (just my biased opinion) BBedit application just to work with Korean text.