This service allows your visitors to vote for your website. It is easy to integrate the service into your web pages. There is no own webspace needed. Where’s the difference? The difference to other voting services is that every user can vote. The users do not need an account to submit their votes.

WP Topvotes

This Plugin let the visitor vote your site via a simple widget like the facebook "I like this" button.

Dwenaus

BuddyPress 1.6 compatible. Users can rate forum posts in BuddyPress. Good posts are highlighted and poor posts diminished. Highlighted karma points shown for each user. Only works with forums for groups; not compatible with site wide forums.
Features & Options: 
* Post rating and responses via ajax. 
* Posts can only be rated once: thumbs up or thumbs down. This can be replaced with ‘like’ and ‘dislike’. Super-admins can rate a post as much as they want, however group admins can only rate once. 
* Good posts are highlighted light yellow (default +10), great posts are highlighted bright yellow (default +25), poor posts become slightly opaque (default -3), and very poor posts have their content hidden and viewable via an ajax link. (default -6). 
* Karma points are given to each user based on their posting history. Karma points can be based on total accumulated ratings (good for quiet sites), average post rating (good for very busy sites) or a balance of the two (good for medium traffic sites). The default is the later. 
* User Karma points are highlighted depending on number of karma points. There are 5 levels (based on natural log). Default, above 7p, above 19p, above 51p, and above 138p. The scale goes from grey to bright yellow. These values can be edited in bp-rate-forum-posts.php 
* Topic ratings are shown in group and forum listings view using the rating of the initial post. 
* Only logged-in users can rate posts. 
* No new database tables are created. 
* Post Karma shows on Member view 
* There is an admin screen to change karma levels, post highligting and diminishing values, and karma calculation method 
* No post rating when the topic is closed (except admin)
Thanks to Intense Debate for their thumb graphics and good layout.

BuddyPress Rate Forum Posts

Users can rate group forum posts in BuddyPress. Good posts are highlighted and poor posts diminished. Highlighted karma points shown for each user.

WP Topvotes vs BuddyPress Rate Forum Posts