When we take in feral kittens from the TNR work, we place them in foster homes for up to a month. The kitten remains in a large cage with food, water, litter box and toys. You have to separate them, or they bond with each other. You want them to bond with humans instead. The foster takes the kitten out and holds it while watching TV, etc, for half an hour 3 times per day. Offers treats and yummy nibbles which do NOT appear in the food dish, so the association is with good things.

Here are a few links for articles on topic:
http://www.alleycat.org/pdf/socializingferal.pdf

http://www.alleycat.org/pdf/Congratulations.pdf

Here is the link to the entire resources list, in case anything else applies to you. http://www.alleycat.org/resources_list.html