Why is $(document).ready not firing for me?

Another cause that will silently fail, and all remaining callbacks never called:

$(document).ready(null);

So check if you have variables or syntax errors that return null. Like this one:

$(document).ready(function($){}(jQuery));

Notice that the function above is called instantly and undefined is returned.

The most likely answer, based on what you have said, is that the core jQuery file is not actually included correctly in the page. You need something like:

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>

Chances are, this is missing or typed incorrectly.