NASA yesterday issued a revised set of dates for 2008 shuttle launches after a meeting to "evaluate options following the STS-122 [Atlantis] mission delay", the agency reports (http://www.nasa.gov/home/hqnews/2008/feb/HQ_08056_Updated_Shuttle_Launch_Dates.html).
STS-123 on Endeavour and STS-124 on Discovery are slated for lift-off on 11 March and 24 April, respectively, although "any decision on those launch dates will take place after the current STS-122 mission lands".
More: http://www.theregister.co.uk/2008/02/15/shuttle_launch_schedule/
Full manifest: http://www.nasa.gov/mission_pages/station/structure/iss_manifest.html