CSS performance: UI with fewer images / Stoyan's phpied.com -
This great little guide gives light-weight, reusable pieces of CSS code that create rounded corners, gradients, drop shadows, and other common UI effects.
Clojure creating Rich HIckey discusses concurrency in Clojure. He walks you through his thought process in designing Clojure for concurrency, and follows it up with a neat little ant simulator example.