This torrent contains 3 PDF books about Linux programming -- 2 of them are open books (i.e. free as in freedom).

The Linux Programmers Toolbox:
Author: 		john fusco
Publish date:		2007
Publisher:		Prentice Hall
Summary: Great book for intermidiate to professional level Linux software developers.


The Linux Kernel Module Programming Guide
Authors: Peter Jay Salzman, Michael Burian and Ori Pomerantz
Publish date:		2001
Publisher:		Internet
Summary: This book is for Linux kernel developers, but it has many interesting parts that would be great for software developers too!

Linux programming guide-0.4
Authors: Sven Goldt, Sven van der Meer, Scott Burkett and Matt Welsh
Publish date:		1995
Publisher:		Internet
Summary: This is an old book, but a lot of the concepts described here are still useful today.