Oldversion
Oldversion.com is a museum that archives older versions of popular software titles. download your favorite old and new versions of windows, mac and linux software.
http://www.oldversion.com
Digg
Not sure how legal this is, but winworld is offering free downloads of old windows versions (1.0 up to 98), various "abandonware" applications and even the legendary microsoft bob!
http://digg.com/news/story/Download_old_operating_systems_and_applications
Vetusware
Vetusware.com - the biggest free abandonware collection in the universe
http://vetusware.com
Oldschoolapps
Old school apps & games is dedicated to bringing you the cleanest, most complete, and enjoyable collection of abandonware games on the internet.
http://www.oldschoolapps.com
Kewlone
Kewlone
http://www.kewlone.com/#rep1
Abandonia
Abandonia
http://www.abandonia.com
Programming Language Archive
Programming Language Archive
http://mitglied.lycos.de/jmksf/misc/pla/pla.html