I suppose most of my readers know that it is pretty easy to get usable computer hardware for free. If the hardware is not fast enough for the latest incarnation of MS Windows, OS X or the some of the recent shoot-em-ups most people are willing to update their hardware to something more recent. If their old hardware happens to be more than, for example, five to seven years old, it is probably impossible to sell at any reasonable price. For people like me, those computers are still more than usable.
Unfortunately, I've not been able to find any real use for hardware that is about 20 years old. Of course, I still could write my text files using WordPerfect 5.1 if I just could find somewhere installation floppies still functioning. Or I could use the computer for playing some classic MS DOS games. Just being geekier than the people around me might be a reason for doing that instead of playing the games using a DOS emulator running under Linux. Or I could use a 386 as a terminal for ssh sessions on some of my more recent computers.
Books, on the other hand, do not lose their value as fast as the computers do. I still enjoy reading books printed decades ago. I enjoy reading Roman and Greek classics in translation and sometimes even in the original language -- if I have some extra time to spend with Latin grammar and old dictionaries.
Even computer books can be useful for decades. I found in the local university library a few old books about AWK, Perl and Emacs that are still very helpful for a semi-computer-illiterate like me. Unfortunately, it is a lot more difficult to find classic O'Reilly books for free than it is to get free hardware. But I'll continue my search for them...
Of course, there are some interesting books that can be downloaded for free, for example the Unix Text Processing by Dale Dougherty and Tim O'Reilly. The book was originally published in 1987 but you can still learn a lot from it if you are just learning to use the GNU command line tools.