Very few things have actually made writing code easier for me. Sure most editors do neat things in the name of helping you do things a bit faster, but rarely does something come my way that truly makes writing code easier. One of those things is "Zen Coding", an extension/plugin for most major editors that makes writing HTML and CSS almost painless.
It simply takes short hand and turns it into full W3C compliant HTML and/or CSS all at the press of a command ( CTRL+e in my editors of choice). Take a look (what I typed is inside of comment tags, results from zen-coding directly below):
(Ugh. WordPress (or SyntaxHighligher?) is eating my HTML doctype, html and head tags from the above example... but they're there I promise!)
It's an extraordinarily cool plugin and I highly recommend it to anyone that writes HTML or CSS on a regular basis.