Hi! So I did a quick google search and found a bunch of websites with basic info about what the test is like.
http://www.ukstudy.com/Show_Front.ph...ContentID=1004 http://www.cambridgeesol.org/exams/ket.htm
The exam is administered by Cambridge U, so the Cambridge Press has a lot of old tests and prepared materials for sale, it seems.
http://www.cambridge.org/elt/elt_pro...asp?id=2500967
There's also a practice test at this next website, but it didn't work on my system so I actually have no idea what it's like.
http://www.examenglish.com/KET/default.php
In the meantime, you can get them started on reading/graphic comprehension with news/journal articles, travel sites, blogs, film reviews, and extracts from the types of books and short stories we read as high schoolers (like Lord of the Flies, Animal Farm, Rebecca), where the language is pretty simple (from what I remember) but they can get new vocab words too. This way you can still direct discussions to current events and other topics if you like.
Also, since part of the test is an interview, you might want to practice interviews by coming up with questions relating to their hometown, families, pastimes, vacations, and so on, for longer than the actual interview would last. Just make sure they're familiar with possible questions and variations (have them iinterview each other), and comfortable with coming up with details on the spot, especially without being asked. Pay attention to their spoken grammar, then you can structure targeted grammar lessons as you go along.
Anyways, I hope I could point you in the right direction at least. As for free mp3's, if you have iTunes, you can check out the English as a Second Language Podcast (I think you can look at
www.eslpod.com too) or ESL Aloud for a few conversations/monologues, but I'm afraid those are the only ones I know of.