Hi - I am sure a lot of people play these already - but I thought I'd put down some of my favourites.
I play Hot Seat a lot as an end of lesson filler - one student stands at the front facing the class (back to whiteboard) and you write some of the target vocabulary on the board. (Eg "I go swimming.") The other students must then tell them what is written without saying the words on the board. Ideally, no Korean should be spoken - so they use a lot of movement and some simple english words (Water! Water!). Sometimes I let them say it in Korean if the student is struggling.
You can also play in teams - by having several students sitting at the front with white boards. First to write and hold up the correct answers gets points for their team.
Blazing pens (unscrambling words and sentences) is another good one. Use a powerpoint with the mixed up words and have individuals from teams writing on the board or give each team a whiteboard. First team with the correct answer wins, natch!
Slow word reveal or picture reveal can also be good. Again, just use a powerpoint with the image/word relating to that day's vocabulary. I usually ask teams to guess in turn about a single image and reduce the points they are going to win each time another hint is given.
A friend suggested Countdown to me (UK tv show - contestants select 7 letters (4 vowels 3 consonants) and the team that can make the longest word wins!) My kids got pretty into it today. I played along with them and they thought that was pretty funny.
http://www.youtube.com/watch?v=e32kaa9TzeE&feature=relatedYou can use that timer to get them into it.
You can also play blockbusters if you draw a letter grid on the board and have a clue for each letter (EG - What R kind of weather will get you wet? RAINY!) First team to get 4 letters blocked off in a row is the winner.
Not a game but they LOVE wordsearches. Candy for the first 3 finished results in frantic scribbling.
A quick game of pictionary/hangman or even charades using that lesson's vocabulary can also kill a few dead minutes at the end of a class nicely : )