helpgeek

By default, the built-in Recent Posts widget in WordPress only allows you to 
display up to 15 recent posts max, even if you specify a larger number. This 
is hard-coded into the WordPress core so any modifications you make would have 
to be redone upon every WordPress update.
No longer!
The Recent Posts Widget Unlimited functions exactly as the built-in WordPress 
widget but without the 15-post restriction. You can now specify an unlimited 
number of recent posts to display without resorting to modifying the WordPress 
core.

Taehan Lee

This plugin make it possible to navigate more recent posts without refreshing screen.
<h4>Features</h4>
<ul>
<li>Navigate more recent posts without refreshing screen (AJAX).</li>
<li>General settings: Title, Number of posts to show, Post title length, List formatting(title, date, author, comment_count, thumbnail), Date formatting, Thumbnail</li>
<li>Filtering: Post type, Taxonomy/Author/Time query.</li>
<li>Navigation: Label, Position, Text align, Page range, Max page links</li>
<li>Effect: Appear effect(Fade In, Slide Down, Slide Up), Disappear effect(Fade Out, Slide Up, Slide Out), Auto Pagination.</li>
<li>Custom CSS, Progress Image, etc</li>
</ul>
Demos: 
http://urlless.com/u-more-recent-posts-demos/
If anything does not work please leave a comment at: 
http://urlless.com/u-more-recent-posts/

U More Recent Posts

This plugin make it possible to navigate more recent posts without refreshing screen.

Recent Posts Widget Unlimited vs U More Recent Posts