Pages tagged internals:

How The Kernel Manages Your Memory : Gustavo Duarte
Moserware: How .NET Regular Expressions Really Work

Knowing how tools you use work under the covers is a huge win for every developer out there and Merb is small and clean enough for everyone to understand it in a short period of time. You can learn a lot about HTTP, web frameworks design and even hidden gems of Ruby web servers (how many of you know that Thin can actually serve requests in threads and not block the event loop?).
A Tour of the Arduino Internals: How does Hello World actually work? - Ideas For Dozens
Fixing Threads in Ruby 1.8: A 2-10x performance boost at time to bleed by Joe Damato
good explanation of Ruby's threads & stack implementation
ruby 1.8 mri assembly threads