I was looking around for the last version of ptkfonted, a bitmap font editor I wrote in the summer of 1999, and continued working on until early 2001. I could find version 0.31, and had nearly given up hope finding the final (and unreleased) version 0.4, but at last I found it deeply buried in a backup of a backup on my office machine's hard drive. Many of the original timestamps were still intact --- at least for things changed after December of 1999, at which time I think my hard drive in my old pentium 90 crashed and I had to restore from a backup, and I forgot to copy with whichever flag it is that preserves timestamps.
Anyway, yay for obsessive packrattery.
To get Perl-Tk to work on windows/cygwin at all I had to download a 3-year-old version of it and pass mysterious arguments to perl Makefile.PL, and of course I was instructed to do this by a cryptic mailinglist post I found through google. Now that sort of experience takes me nostalgically right back to my early undergrad unix-hacker days of 1999 or so if anything does.