I have to agree with all the posts above - by far the best I have found is Talk to Me in Korean.
The lessons are easy, short and well put together with PDF and audio, they also have a bunch of videos that you can watch about random other things like colors, numbers and other things.
I like that they take the time to pronounce the words really slow, they say them many times at different speeds so you can really hear what it should sound like and imitate. I have tried a few words out at work with my Korean colleagues and they have been really impressed with my pronunciation.
I also like that they are quite short, especially at the start. You just learn one or two things, thats good if you don't have much time and if you do you can always just go onto the next lesson. I am not very good at remembering things so its nice that its just a little bit each time then I can work on memorizing it before I go onto the next bit.
I have just seen that they have a new pay site and among other things you can post your sentences on there and they will check them and correct them if need be.