The OnEarth server for MODIS is currently being phased out and replaced by the Global Imagery Browse Services (GIBS) provided by the Earth Science Data and Information System (ESDIS) Project: http://earthdata.nasa.gov/gibs. Daily, full-resolution mosaics are generated in near-real time for 50+ imagery products and available through OGC WMTS, Tiled WMS, and KML generation services. The Worldview client (http://earthdata.nasa.gov/labs/worldview/) can be used to interactively browse all the imagery provided by GIBS.
The OnEarth server no longer provides full WMS services for any of the datasets that it originally hosted. Tiled WMS access, described in the Tiled WMS and Google Earth KML support pages will stay operational in the near term, including access to the archive of MODIS daily mosaics from 2006 to the end of 2010.