The Challenge Magazine PDFs are excellent digital reproductions of this classic RPG magazine. The page and cover scans range from good to excellent quality (the covers may show some signs of wear from the original), and all text is fully searchable. I just wish they had gone the extra step to bookmark them as well.

This particular issue has a wealth of information for Twilight: 2000, Traveller: The New Era, Lost Souls, Cyberpunk, Dark Conspiracy, Call of Cthulhu, GURPS, Space:1889, Shadowrun, and the West End Star Wars RPG.