This plugin by Ali Hussain was made specially to help people using wordpress insert adsense or any other advertisement in the wordpress blogs in whatever position[1] in whatever post[2] they wished.
[1] above and below content, above and below post titles [2] positions as in below post 2, above post 4, below post 5 whatever position does the blogger wish.
The author has posted some images at: http://www.flickr.com/photos/alijiwani/sets/72157625713524678/
Download and info: http://wordpress.org/extend/plugins/adsense-custom-placement/