When I first started studying Korean, I used Korean online dictionaries exclusively, either Daum or Naver or my cellphone dictionary. Later on, figuring I needed a portable dictionary (and also to support my Korean drama addiction) I bought a Iriver dictionary.
The Iriver dictionary was useful but once I got my laptop and started going everywhere with it it became less useful. When I got an ipod it became even less useful — there was no way I was going to carry an ipod, a laptop, and an electronic dictionary everywhere I went. And I found out that the dictionaries available for the ipod were much better than the Iriver ones.
Now I don’t use my Korean cellphone (naturally) since I’m in Israel — so if I’m on my laptop working and there’s internet access I continue to use Daum (and sometimes Naver).
However when I’m computer less I depend heavily on my ipod dictionaries.
Which dictionaries do I use? Probably the dictionary I use the most is the Prime Doosan Dong-A Kor/Eng 두산동아 프라임 영한/한영사전. It’s an Korean-English, English-Korean dictionary with tons of example sentences.
The dictionary I use the second most is Donga’s Prime 표준국어 사전. It’s a massive Korean-Korean dictionary. I should use it more than I do but these days usually when I’m looking up a word I’m usually looking it up English to Korean.
Another dictionary that I like a lot but don’t use very much is 우리말 한자어 속뜻사전 which is good for searching up the hanja in different words.