Used book store, pick up the ones you can't live without for a buck or two each?
Edit: I worry about that with my work stuff. Our project management is something we've more or less "farmed out." All the project information is stored remotely: client details, contact information, lists of procedures done, copies of e-mails, etc. We have some stuff stored here, our e-mail is backed up locally, but it isn't sorted by project, and each individual has their own e-mail account, so there's no central repository. There's paper copies of a lot of stuff too, but that's cumbersome to wade through, and not as complete. Data is all backed up here as well, but it would be difficult to reconstruct what project is what without the software to tell you.
It's kinda the key to everything.
Edited, Oct 24th 2013 9:35am by someproteinguy
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That monster in the mirror, he just might be you. -Grover