Under The Hood Look At Shared and Static Libraries, Linkers and Loaders

Linker Loader :
Link order of libraries ,
Link options for gcc ld,
Yolinux Tutorial on Static, Shared Dynamic and Loadable Linux Libraries,
Shared Library How-to,
How-to write Shared Libraries by Ulrich Drepper (Redhat),
Cross Platform Shared Library How-to ,
Program Library How-to,
Linkers and Loaders online downloadable book 

Howto Look Inside Executables, Libraries and Object Files

Object file commands :
strip,
ld,
objdump,
nm ,
objcopy,

Blog on How to Use Objdump to look inside Your Program
Unix Tools for inspecting Object files (article on LinuxJournal),
The ELF Object File Format by Dissection,
Wikipedia on Executable File Formats

Understand Source Code by Reading Code and Refactoring for Maintaining Large Projects

This list consists of one-liner tips to be used for easy lookup and reference.

Rewriting Code for Better Understanding (Coding Horror)

• What I cannot create, I do not understand. [Richard Feynman]
• "What I do not create, I do not understand."[Chris]
• "It's easier to understand 600 tables than 100,000 lines of code." [PaulC on comp.databases.theory/2005]
• Create a new project with blocks of code copied from old code. Refactor to reduce "old code smell"
• Start refactoring by adding small tests to better understand code and act as regression tests.
• Just scan through huge amounts of code till it starts making sense - "understand by constant exposure".
• Create a text file to capture your understanding - briefly describe how the component works, realtions to other components, what it persists, its states, and source browsing/debugging tips you found useful.
• Manually reformat a copy of the code - white space, and indented as per your personal style.

References:

1. Working Effectively with Legacy Code
2. Object Oriented Reengineering Patterns
3. Refactoring: Improving the Design of Existing Code