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.

Eduard Milushi

This plugin will generate a widget for you website where you can show latest posts of your blog with thumbnails and choose to show ads between posts for every X post(you choose it ), you can select to show or hide post date, comments count and the total number of posts to be shown, when the widget is active on single post view the current post will be ignored from the list. All posts are sorted by latest post date. As well you have a text area where you can add you’r ads code, html and js is accepted so you can put your banner or any google ads code.

Latest Posts With Thumbnails and Ads

Just like the default Recent Posts widget except that posts are with thumbnails and you can show ads between them, show post date and comments count.

Recent Posts Widget Unlimited vs Latest Posts With Thumbnails and Ads