Up to 276 at the moment:
http://www.onemanga.com/Kekkaishi/
http://mangashare.com/manga/Kekkaishi

If you're looking to catch up, I think now would be a prettty good time. Yoshimori is finally becoming a bit of a badass and kicking some ass. We also learn the real nature of Karasumori, though it has been hinted at quite a few times.