Sergey.S.Betke

When your blog is loaded, all links of this class .more-link (standard wordpress css class for “Read more…” 
links) are modified to no longer send the user to that post’s 
single page display when clicked. Instead, the WordPress database is queried for that specific post, and all content 
after the <!–more–> tag (i.e. only what you need) is returned. 
The new content is then immediately displayed to the user with light animation (You can disable animation in plugin options), 
inline with the opening content.
<ul>
<li>AJAX-read-more uses the jQuery framework already included with WordPress installations.</li>
<li>This plugin used GET ajax action (not POST, like other plugins), wordpress “template_redirect” action.</li>
<li>It’s compatible with cache plugins (like Hyper Cache Extended).</li>
<li>AJAX-read-more: design of progress indicator and other behaviors – by CSS (example – in css/all.css)</li>
<li>cache-safe script and css url</li>
</ul>
Check plugin options on options page.
Thanks for debugging to den@10-13.ru.
Theme requirements:
<ul>
<li>Your theme must generate correct DOM structure: 
(div id=”#content”) 
… 
(div class=”post”) 
 … 
(/div) 
(/div)</li>
<li>Theme must support footer (wp_footer). If not, you can change corresponding option on plugin option page.</li>
</ul>
For more information, please visit the <a href="http://sergey-s-betke.blogs.novgaro.ru/category/web/wordpress/read-more" rel="nofollow ugc">Sergey S. Betke blog</a>.
<h3>ToDo</h3>
The next version or later: 
* wordpress core integration for cache headers processing??? 
* optional http cache-control max-age header value and must-revalidate 
* just private cache headers, when post has limited access 
* check cache plugins support (Hyper Cache Extended): clear cached responces when post modified 
* cache-control and Last-Modification headers – to separate plugins 
* if-modified http request support (separate plugins) 
* the_excerpt optional support 
* AJAX-read-more send correct http cache-control headers, and fully support client-side public cache. 
* WP 3.3: http://wpdevel.wordpress.com/tag/3-3-dev-notes/ 
* WP 3.3: replace wp_localize_script() with wp_add_script_before(). wp_localize_script doesn’t support non-string params in WP 3.3+ 
* WP 3.3: wp_enqueue_script() now works mid-page – insert scripts just into pages when it’t needed

AJAX Read More

Automatically transform your  links into links that immediately display the rest of your entry (AJAX).

Xoda

Random Post Box is a plugin that lets you place a box anywhere on your blog, with template tag or shortcode, and 
load random posts with an interval and fade effect. It uses jQuery (Ajax) which means that the content is loaded without 
loading the rest of the page. The timings can be set in the admin options-panel.
The template tag is <code><?php random_post_box(); ?></code>. You can also use the shortcode <code>[random-post-box]</code> in a page or post.
<h4>Features</h4>
<ul>
<li>Insert placeholder with template tag</li>
<li>Insert placeholder with shortcode</li>
<li>Set time for displaying the post</li>
<li>Set times for fade in and fade out affect</li>
<li>Exclude or include posts by category</li>
<li>Exclude posts by age (in days)</li>
<li>Use title only</li>
<li>Use post excerpt or bodycontent</li>
<li>Strip tags from body</li>
<li>Show/hide post metadata</li>
</ul>

Random Post Box

The Random Post Box plugin places a box anywhere on the blog, where it loads random posts one-after-the-other.

AJAX Read More vs Random Post Box