Would be nice to have archives of some mailinglists (-dev, -project, -user at least) available as mbox or tarball of maildir or any similar machine-readable format. Since there's (afaict) no private information in them it should be a public-accessible URL, maybe plain http. Maybe even regularly updated for extra fun?
"no private information" -> email addresses need to be spam-protected, so we're not offering this publicly. You won't find unredacted mboxes from marc/gmane for the same reason. Give me something that does a good automatic redaction, and i'll set up a monthly cronjob to export COMPRESSED mbox files of mail for you; FYI all of lists comprises about 30GB uncompressed presently.
gmane does offer an nntp gateway where you can get raw mbox archives. they might be slightly munged (s/@/ at / sort of thing), but that's it, and pretty trivial to undo.
archives.g.o ?