The Transportation Security Administration has installed the new "backscatter" screening machines in many airports, but a good number of them aren't actually used yet. One helpful site is compiling reports on which airports are still using X-ray/metal detector combinations.
Ari Ofsevit went through an "enhanced pat-down," and reported on it, but came to notice that some airports weren't requiring either the new scanners or pat-downs—they were keeping with what now seems like old-fashioned, post-9/11 security measures. To share those airports without new machines, or with idled installations, he's created a page listing airport codes and color-coded status reports of their use of newer measures.
You can keep Ari in the know about your own travel experiences by emailing [email protected] or tweeting at @tsastatus.