I hope this link works but I found this one to be helpful. I never got a chance to build it but it seems semi-easy.

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

if this link doesn't work then you can try this link:

http://www.alleycat.org/resources_list.html

and click on "Build an Inexpensive Cat Shelter" link.

There is also this one:
http://www.alleycat.org/pdf/feeding.pdf
and if that link doesn't work you can go to this one and click on "Feral Cat Feeding Station"

Thanks for helping the strays.

Melissa