Hillsdale College now has the complete writings of William F. Buckley Jr. archived and searchable online. I'm assuming, given all the restrictions that would normally apply through copyright law that Buckley must have helped arranged this--or at least signed off on it. It could be his final, and possibly greatest gift.
John Wohlstetter at Letter from the Capitol says that the transcripts of Firing Line programs are available at the Hoover Institute, but I'm not seeing how you can get them. A few of the programs are digitized and available in RealVideo, VHS, and DVD format. Let's hope Hoover has the resources to get the make the rest of them available.