post interesting open source physics texts?

[orange31]

Hello, I came across these, very different but pretty neat, for novices especially who still want the math-

I'll post also in the 'recommended books' sticky, but as these are actual downloads, I thought it could stand alone as well-

Lieber, 'The Einstein theory of Relativity'.
Ancient, but that's good for beginners as it goes thru the math step-by-step

http://www.archive.org/details/einsteintheoryof032414mbp

Christoph Schiller, Motion Mountain, huge 1600 page physics textbook

http://motionmountain.eu/download.html


Any others? thanks in advance.