Official Korea Tourism Website The website is super useful! You can request for a booklet and map to be sent to you for free! You can also book a goodwill guide for free! http://english.visitkorea.or.kr/enu/index.kto
Filming LocationsFamous Korean movies' and dramas' filming locations can be found at http://english.visitkorea.or.kr/enu/CU/CU_EN_8_5_1.jsp. The Cofffee Prince shop was overpriced, but still adorable.
Changdeok-gung PalaceIf you have limited time, just visit this palace... the largest and the most beautiful. The entrance fee is only W3,000 and you get to dress up in traditional Korean hanbok for free! With the palace as the setting for the photos, you'll really feel like a princess in a Korean drama ^^

N-Seoul TowerIt's possible to either take a cable car or walk up 2km. You should walk, because you get to take photos at a very scenic spot halfway up the hill.

There are martial arts performances on top of the hill sometimes. There's also a food court, the teddy bear museum and the famous locks from “We got married”!
DMZ TourJust sign up with any domestic tour agency... the tour is quite interesting as you get to walk through the low tunnel dug by the North Koreans, and glimpse North Korea.
Suwon Folk VillageTake a 1 hour ride on the subway to Suwon. The folk village is very big, and was the filming location for “Jewel in the palace” and “King and the clown”! There's really fun places to take photos e.g. in jail cells, being caned in front of the magistrates' court. There's also performances like see-saw jumping, tightrope walking etc

Jimjilbang!I went to the 7 storey Dragon Hill near Yongsan station with some newly-made friends. There's ginseng bath, jade bath, charcoal sauna, ice room, games room, movie theatre, swimming pool etc… all for just W 12,000! Be warned about trying to crack a hard-boiled egg on your head though ^^
Tax RefundOnly need to spend over 30,000 won in a receipt! You can even claim for groceries^^ Do claim so that you can pay for excess baggage charges.