You might be aware that we are running a public instance of CRX (Day's JSR-170 compliant repository) at http://jcr.day.com (the login is admin/admin). As of today there is also the CMIS interface (Atom binding) to that repository publicly available at http://cmis.day.com. The underlying code is the version from the CMIS plugfest, but expect frequent updates. Feedback is appreciated (either as a comment on this post or to mmarth (at) day (dot) com).
