Of course I started putting food out for them. And then today I discovered Home Depot having a sale on storage, so I picked up a couple 18 gallon rubbermaid totes for $4 apiece, and a bale of straw. A little bit of surgery with a circular saw has converted the totes into adequate cat shelters:
Tomorrow morning I'll stuff them with straw and put them outside (weighted down with cow skulls because, um, that's what I have to weight them down with) and hopefully the kitties will get some use out of them this winter. In summer I will probably cover them with reflective blankets to keep them cooler inside. Also I need to figure out awnings over the entrances to keep the weather out better, but for now, with the horrible cold snap we're having in the south, they will suffice to get kitties out of the cold!