Led Zeppelin will re-release their first three albums on June 3. Guitarist/producer Jimmy Page has remastered each album. The band plans on releasing remastered versions of all their albums eventually.
If you want the "deluxe editions" of these albums, you will get previously unreleased material on companion discs.
Page says, "The material on the companion discs presents a portal to the time of the recording of Led Zeppelin. It is a selection of work in progress with rough mixes, backing tracks, alternate versions and new material recorded at the time."