jQuery and WordPress Theme/Plugin Development

After toying around with Prototype, I decided to take a look at jQuery and in particular the jQuery Validation plugin:

http://docs.jquery.com/Plugins/Validation

I have hit a snag with loading the built-in version of jQuery using wp_enqueue_script('jquery'). The $() functions return “property does not exist” errors. I noticed in the header of the Admin pages that they make a direct call to jQuery() to work with the dashboard feeds.

My workaround so far has been to just load in a vanilla version of jquery.js, but I am curious if there is a general guideline for using jQuery in WordPress plugins or themes that would differ from the native documentation and tutorials.

Page in question: http://stephenyeargin.com/contact/

Other references:
http://codex.ww.wp.xz.cn/Function_Reference/wp_enqueue_script