Some links that might be of use to developers ...

Programming:

• Structure and Interpretation of Computer Programs
• How to Design Programs
• The Art of Unix Programming
• Secure programming for Unix and Linux HOWTO
• Beej's Guide to Network Programming
• Beej's Guide to Unix Interprocess Communication

Algorithms:

• Handbook of Applied Cryptography
• Data Structures and Algorithms
• Data Compression

Languages:

• Beej's Guide to C
• PHP Manual
• PerlDoc
• Python Documentation
• Dive Into Python
• Java Documentation
• Mono (.NET) Documentation
• Art of Assembly
• Advanced Bash Scripting Guide
• Schemers.org

Operating Systems:

• Single Unix Specification, version 3
• The L4 microkernel family
• QNX Neutrino
• Plan 9 from Bell Labs

Misc:

• Internet RFC Index
• Internet FAQ Archives
• The Linux Documentation Project
• Game Development News & Resources