I feel bad for not sharing this map... I must have seen it back in November, but I totally forgot to share. It's very English friendly; whoever made it wanted to include foreigners as well. It has gay places not only in Seoul, but also most large cities in the ROK.
You can search by location or category. For example, maybe you wanna go cruising in Seoul. Apparently you can over at Guro Digital Complex. The more you know.

Some of the English is a bit off (I think by restroom they mean cruising sauna for example), but that's ok. Looks like I've got some more gay areas (gayreas?) to explore.

Check out http://www.koreapinkmap.com/ for gayness near you!