Developer tools:
http://www.sitepoint.com/alcatraz-the-package-manager-for-xcode
http://incident57.com/codekit/
http://net.tutsplus.com/articles/general/textexpander-for-web-developers/
http://net.tutsplus.com/tutorials/ruby/how-to-install-ruby-on-a-mac/
http://net.tutsplus.com/tutorials/tools-and-tips/essential-textmate-shortcuts-tips-and-techniques/
http://net.tutsplus.com/tutorials/tools-and-tips/quick-tip-use-textmate-bundles-to-increase-your-productivity/
http://net.tutsplus.com/articles/general/expedite-your-workflow-with-macros/
http://net.tutsplus.com/articles/web-roundups/20-mac-apps-youll-use-every-day-editors-choice/
http://net.tutsplus.com/articles/news/learn-how-to-be-a-textmate-champion-new-plus-tutorial/
http://net.tutsplus.com/articles/web-roundups/30-amazing-mac-apps-for-developers/
http://net.tutsplus.com/articles/web-roundups/10-apps-for-developers-on-a-shoestring/
MAMP
MAMP on all platforms
You tell LiveReload to watch a particular folder. When any file in that folder changes, it triggers preprocessing. It can do a whole bunch of preprocessors. For CSS: LESS, SASS (w/ Compass), or Stylus. For JavaScript: CoffeeScript or IcedCoffeeScript. For HTML: HAML, Jade, Slim, or Eco.
LiveReload
http://www.sitepoint.com/livereload/
LiveReload on AppStore
More about LiveReload