Razesdark

This plugin will allow all authors to have their own tweets shown on in the widget area of their posts, by adding it to their profiles. 
That way any multi-author blog can let their bloggers promote their own twitter account and not a joint account.

Author Based Twitter Widget

A Author based twitter widget, made to help multi author blogs have individual twitter widgets for their authors.

jgwhite33

Allows you to insert a listing of related Amazon products, on the single post page by using a custom field called amazon_search and inserting simple code in your template file. 
The listings are completely customizable according to parameters defined in the admin panel. If you include an Amazon Associate ID, you can even earn commission! Also allows you to share revenue with your authors on a multi-author blog. Whoever wrote the post gets credit in the listings. Creates a custom field on the author profile pages so they can input their campaign ID. Whoever wrote the post gets credit in the listing.
A few of the features:
<ul>
<li>Specify the search with a custom field in the post called amazon_search</li>
<li>Allows you to use the Amazon Associate Network</li>
<li>Allows multi-author blogs to share revenue, you can even specify the percentage to share</li>
<li>Can share revenue with the author of the post if you desire</li>
<li>Uses advanced search parameters</li>
<li>Display is easily customizable</li>
<li>Hides the affiliate link to Amazon</li>
</ul>

WP Amazon Ads

WP Amazon Ads - allows you to easily insert Amazon product listings into your WP posts, and earn commission from sales.

Author Based Twitter Widget vs WP Amazon Ads