Note: This post is out-dated as of July 28, 2010 and the release of Safari 5.0.1 in which extensions are enabled by default. Check for updates in Mac OS X and upgrade to the latest version of Safari.
Sometimes we just assume that everybody knows everything that we do, but I’ve seen a few people ask the simple question, “How do you enable extensions?”
So let’s get back to basics for a minute and talk about how to install safari extensions.
Even if you already have extensions installed, skim this, there’s an interesting bit.
Extensions are not enabled by default in Safari 5, and they’re well hidden at that.
1. Advanced Preferences pane and 2. Enable the develop menu.

3. Enable Extensions in the Develop menu.

4. You’ll now see the extensions tab in preferences where you can manage (configure, disable, uninstall, and update) your extensions.

Feeling Lazy?
Or, if you’re feeling lazy, you can try this Applescript that does the whole process for you.
@jwisser I've compiled a little apple script to enable safari extensions: http://cl.ly/1OHs

(I’m just a little disappointed that it doesn’t mention us.)
Bonus tip: There’s no reason to keep the Develop menu cluttering your menu bar if you don’t need it. You can disable the Develop menu and that won’t affect Extensions. They stay enabled even with that menu gone.
Now what?
Next, go find some great extensions in our Safari Extensions resource area.
