Everyone who knows me knows that I love maps. And I love online maps, too, and the amazing things that can be done with them, for example, google earth. Unfortunately, google earth, yahoo maps, and related "international" (really, US- or Europe-based) mapping websites don't have very good data on Korea's mind-numbingly complex urban geography. Google earth, for example, is inconsistent in their romanization of Korean place-names and therefore it can be impossible to find locations because one has no idea how the google-earthians might have spelled them.
But, in fact, there are excellent online mapping resources for South Korea. Every single Korean vehicle has a GPS-using map-o-matic device of some kind on the dashboard, which delivers down-to-the-building navigation information. It's definitely out there. The problem is that it's not in translation. You've got to be willing to work in Korean.
So, recently I have begun to feel competent using naver.com's map section. I have figured out bus routes, located ATM's for my bank (외환은행), and located "addresses" (not street-number-based, as in the West, but rather based on "block numbers" and neighborhood names). It's extremely cool, and I can spend hours poking around with it.