Here are five on-line books of lecture notes on solid mechanics, continuum mechanics and finite elements. They are primarily a teaching resource for engineering students at the Department of Engineering Science, University of Auckland, but anyone is free to use them (but see the Creative Commons licence below).
Please send any errors, typos, comments, etc. to firstname.lastname@example.org (I am always interested to hear who is reading these notes, and where you are from).
To reference these notes, see here.