Project Gutenberg (referring to the printing press that originated in the fine German town) is an online collaborative community project to collect a large number of copyright expired texts in a freely available online form.
People do OCR and manually fix the pages up (and add a whacking great disclaimer OfDoom?), to create a huge reference source of many classic texts from the beginning of the TwentiethCentury? and earlier.
(Isn't copyright expired an odd term, since actually it means that everyone on earth just gained the right to copy. Oh well.)
Some oddness results from different territorial laws regarding the copyright status of various texts. That which is legal here may not be legal where you are, and ViceVersa?.