Here is the best site in English for all of the races. Then to register, you'll probably need a Korean friend. Or depending on where it is, sometimes the race coordinators speak English and can help you. Hope that helps! http://www.seoulsynergy.com/seoulmarathonraces.htm
that seoul synergy site is for last year if you look, apparently they now specialize only in triathlons. the website i use (yeah its in korean) is http://www.run1080.com/guide/guide_02.htm#09%EC%9B%94 if you can read korean its pretty easy to find the link to the homepages for most of the races. now many of them have english websites especially the bigger races. there are foreigner groups here that do group signups for some bigger races. I got signed up for 2 races through the haebongchon running gnus
maybe the folks at the seoul flyers can help getting an english site up, i know that would be a huge help. I've tried to get the seoul global center interested in this but no luck
Chuck - Thanks for the info...just wondering how you found out about the groups that help foreigners sign up. I'm really interested in doing more, but I find it is so hard to know where to look. Thanks!
i actually met the woman in charge of the haebongchon group at the gym (samwon fitness in itaewon) she was working out the same time i was and was putting up posters for the hbc run in june and told me about the facebook group. seoul flyers also does it for their members and they have a link on this site.
the rest? I usually have my office assistant help out reading the korean. i'm getting a new one for the upcoming semester i hope she can still help.