The new launch date for the TacSat-3 mission is May 19 with a backup day of May 20. The launch window for both days is 7:35 to 11:30 p.m EDT.
I have complete information on the special payloads being carried on this launch here on the Milcom Monitoring Post blog at http://mt-milcom.blogspot.com/2009/05/rocket-set-for-launch-on-virginia.html