The hearing is happening now, and can be viewed over at the Judiciary Committee's website or at C-SPAN.
The witnesses from the Privacy and Civil Liberties Oversight Board will be:
The Honorable David Medine
The Honorable Patricia M. Wald
The Honorable Rachel L. Brand
The Honorable James X. Dempsey
The Honorable Elisebeth Collins Cook
We'll post any written testimony as it becomes available. (A statement from Senator Patrick Leahy, the Committee's Chairman, can be found here.)