FalconLog des Dragons There are only two left, NASA uses them for various types of research projects and to monitor the shuttle launches. I believe they have EO/IR sensors (fitted to the nose and movable, think of a super-ATFLIR/LITENING) that can cover the shuttle's ascent from high altitude and check for debris coming off that could damage them.
I believe the reason NASA still flies them in addition to the ER-2's (NASA's U-2's) is that they have a much larger payload capacity/flexibility and the backseater adds a bit of flexibility to the mission.
Official site, with specs, pics and missions:
http://jsc-aircraft-ops.jsc.nasa.gov/wb57/index.html
The WB-57 was working with a NRL NP-3D to make geologic maps of Afghanistan. The maps were to assist the people of Afghanistan make roads, look for oil, and do something with their economy other than heroin. See attached link for more info:
http://afghanistan.cr.usgs.gov/airborne.php
