I too had a terrible infestation of crazy ants - multitudes of nesting sites outdoors (trees, stumps, power line poles, etc), with numerous places where they were starting to infiltrate the house. It was remarkable!
I read through all the comments in this thread, and two people provided the absolute best remedy given my experience: Termidor SC which consists of fipronil.
The ants walk through the dried spray (outside where you spray) and it contaminates them but does not kill immediately. They take it back to their nest(s) while contaminating each other ant-to-ant. The nest(s) and queen are dead within days.
The product is very easy to apply outside, but be sure that conditions are dry, and will be for a day or two after application. It is available online, such as Amazon, but I usually buy it from these people:
http://www.domyownpestcontrol.com/termidor-sc-p-184.html?gclid=CL3d9OjrptACFZSEaQodEdoDDQ
This will solve your problem efficiently and affordably.
Thanks!