Computer Networks and Internet
Internet working with TCP/IP Volume III
The Linux Programming interface
Computer Architecture: A Quantitative Approach
Operating System Concepts
Computer Networking: A Top-Down Approach
W. Richard Stevens (Somewhat out of date, but I haven't seen anything to beat them.)
Doesn't look horrible: http://intronetworks.cs.luc.edu/
Computer Networks and Internet
Internet working with TCP/IP Volume III
The Linux Programming interface