Very easy way to add a Related Posts widget.

http://brps.appspot.com/

SnapABug is a widget that can simply be installed on any website. It enables users to easily request support while providing the support team with a screenshot of users web page along with additional debug information; Helping website operator to help their customers faster and more accurately. The SnapABug Help widget is free.

http://snapabug.com

Modpoll is a free service that let's you easily create and manage polls. You can create as many polls as you'd like and add them to your blog or website. You can either add polls individually to your site or add one time code that automatically displays your most recent published poll on modpoll.com.

http://www.modpoll.com

FoxRecord are small one-click embeddable widgets that provide you with a way to rank your website/blog pages by popularity between your visitors. The widgets meld with your site's original look and feel, appearing as a native part of your interface. Pages that utilize FoxRecord automatically receive trackback links from the main FoxRecord page, advertising your pages over Internet and guiding even more visitors to your website. Give it a try - it's fancy - we promise! :)

http://foxrecord.com

TwitSnap is a FREE widget that automatically provides Twitter status preview of a user. The widget will automatically parse your page and look for the @pattern, convert it into a link to user's profile on Twitter and then provides a preview of the user's most current status via a pop-up dhtml box.

http://www.twitsnap.com