It seems to me that every hotel in Seoul is more than US$100 per night for 2 people. As we are trying to travel Asia on a budget, does anyone have any ideas about how to find budget accommodation in Seoul (less than $100, and better if it was around $80)?

Try Asiaoz, they might not have the lowest budget places but probably have lots under $50-90.
To save searching try this, click on the sort by price, might be of help:

http://b2b.hotelclub.net/Enter.asp?i...asp%3Fid%3D163

I have found a cute guesthouse for approx. US$ 40 per night. I had a friend check it out and she says it is clean, basic and friendly. I shall report back to this forum with the results of my stay.

might be a bit late but here's a guesthouse my friend stayed before and they find the owner friendly and most impt of all, right in town n near the subway

http://www.mdguesthouse.com/

The USO base has a good inexpensive hotel attached to it. I actually stayed at the Kaya which is about a block away (sometimes listed as 'Gaya') last October for $55 a night and thought it was very nice. I went over to the USO for breakfast every morning, and as I was traveling alone, it was SOOOOO nice to have people who spoke English and could answer questions.

The Rainbow is also close to the Kaya and the USO on Camp Kim. We've stayed there several times and enjoyed it (@$55/night.) Both the Kaya and the Rainbow take overflow from the Dragon Hill Lodge and are very familiar with Americans (i.e. English speakers.)