I don't know where to find a current inventory, but I think they now keep four US EMUs on the ISS. They've been dealing with various failures, and at one point were down to 2 working ones, but I believe there are 4 functional at this time: 3003, 3011 (the one that tried to drown Luca), 3010, and 3005. Dragon I think took up 3003 and returned 3015 during CRS-3.