I’ve been using Subversion for many years, probably since 2002 or so, and when I started using it, I imported my existing CVS repository, which contains stuff dating back to 1995 or so. It’s a big and (to me) very valuable archive, especially since I started early on to put all sorts of stuff in there – not just source code, I mean, but rather everything that may be versioned, and that just benefits from being backed up in that repository. All my business paperwork, things like that.
(As an aside, I’m regularly surprised that many people don’t seem to do anything similar – what do you guys do with important documents that aren’t source code? Every now and then I have this discussion where somebody has the opinion that a source control system only needs to be integrated nicely with Visual Studio to make them happy, and I find that position extremely weird.)