I would consider being part of this idea. I still have all of my old Amiga magazines (probably around 65-70 issues spanning about 5 years: 1989-1994 sound about right?). I think .pdf is a cool idea, but it is true that to do a good quality one of an entire magazine will result in a pretty large file. It's hard to say what will work best. I'd probably lean towards the individual .jpgs so that someone can choose via thumbnails which ones they want to view (that's assuming you want high quality scans...)
