According to Dana Priest, WashPO on Thursday,  16 Feb 2006:

Washington, D.C.: To your knowledge, does the Vice President really have the authority to just declare material unclassified?

Dana Priest: Lots of questions on this one so I turned to my classification guru, Steve Aftergood, at the Federation of American Scientists. Answer: 1-The VP can declassify anything that his office classified or generated initially. 2-The VP can declassify other executive branch information only if the president has given him implicit or explicit authority to do so, which is not self-evident in Executive Order 13292 of 3/25/03 3-not even the president can declassify everything except information protected by statute: certain nuclear weapons secrets, sources and methods. For more, go to www.fas.org/blog/secrecy. A great site. So, the bottom line is, we'll probably have to get the president to answer whether he delegated this to the VP, and/or if the information in question was generated from the VP's office.

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Executive Order 12958: A Renewed Focus on Declassification

In 1995, with the stated goal of "seeking to bring the system for classifying, safeguarding, and declassifying national security information into line with our vision of American democracy in the post-Cold War world,"President Clinton signed Executive Order 12958. Under this Order, records over 25 years old will be presumed declassified beginning in the year 2000 unless an agency acts to keep them classified based on an exemption provided in the Order. Agencies were given five years to complete their review of these older records, and in the Order’s first year were to complete a declassification review of 15 percent of the records subject to the Order.

 

Thank you all for the information you gave me.  I appreciate all who responded.

Froomkin's White House Briefing provides some useful information:

"Cheney was referring to an executive order on classification of information first signed by President Bill Clinton in 1995. In March 2003, just days after ordering U.S. troops into Iraq, President Bush amended [the] order to, among other things, give the vice president the same classification power as the president."