There are many, many Social Bookmarking options available for WordPress, I have tried to sift through as many as I could to give you the best 20.
My favorite is Sociable, which I use on this site. That is not to say it is the best, the idea is to find the plugin that best fits into the theme and style of your site.
I hope these help.
Description: Sociable is a plugin which adds social media buttons to your posts, and does so easily, and beautifully.
Note: This is the plugin I use for speckyboy.com.
Download: Sociable WP Plugin Download.
Description: ShareThis makes a WordPress plugin that provides an unobtrusive way for your visitors to post your site content to various social bookmarking sites, or send a link via e-mail & other communication channels (like Facebook and MySpace) to a friend.
Download: ShareThis WP Plugin Download.
Description: Helps readers share, save, and bookmark your posts and pages using any service, such as Delicious, Digg, Facebook, MySpace, and all the rest. The button comes with Add to Any’s customizable Smart Menu, which places the services visitors use at the top of the menu, based on each visitor’s browsing history.
Download: Add to Any WP Plugin Download.
Description: obsocialbookmarker is a social bookmarking plugin which adds user-submission links at the bottom of each post for various social bookmarking sites which allows your visitors to easily submit them in a number of social bookmarking sites.
Download: obsocialbookmarker WP Plugin Download.
Description: I Love Social Bookmarking is a simple WordPress plugin that allows your readers to submit your content to social media services via a clutter-free drop-down list of attractive icons.
Download: I Love Social Bookmarking WP Plugin Download.
Description: A simple and light plugin to add social bookmarks buttons to post and pages. I’m focusing in collecting non-english bookmarks services.
Download: Bookmark Me WP Plugin Download.
Description: Social Bookmarks is a WordPress plugin that adds a list of XHTML compliant graphic links at the end of your posts that allow your visitors to easily submit them in a number of different social bookmarking sites. It features an AJAX front-end interface.
Download: Social Bookmarks WP Plugin Download.
Description: FreeTellaFriend is a free service to allow your visitors to share your website with their friends using a click of a button. Once you placed our button on your pages, your visitors can click the button and start sharing. It’s much quicker than the traditional way.
Download: Tell a Friend WP Plugin Download.
Description: A really simple plugin that will add bookmark links of Del.icio.us, Digg it, Slashdot, RawSugar, Yahoo! MyWeb, and many other links to your wordpress. You can decide which bookmark services you want to show and in what order. You also can define, a own iconset.
Download: SociBook WP Plugin Download.
Description: The Social Media Marketing Plugin that lets you put social bookmarking links in your posts and other pages. Help your readers promote your blog and watch your traffic grow.
Download: Bookmarkify WP Plugin Download.
Description: Icons for major Social Bookmarking websites: Digg, Reddit, del.icio.us, dzone, stumbleupon, blinklist, blogmarks, furl, newsvine, technorati, magnolia, google, myspace, facebook, yahoo buzz. More to be added in the next versions. -”mac effect” – when the mouse is over the icons they grow. -Administration Panel to select only the desired Social Bookmarking sites.
Download: SocioFluid WP Plugin Download.
Description: Hocus Pocus Buttons is a WordPress-Plugin that provides sidebar widget with a widerange set of buttons for social bookmarking websites. However each button is only visible to the user if he has visited the corresponding site lately.
The goal is not to disturb the user by using too many buttons / links (since he could probably only use one or two at all) and rather only show relevant services.
Download: Hocus Pocus Buttons WP Plugin Download.
Description: 17fav Bookmark & Share WordPress plugin allows users to add your post to many social bookmarking and share sites.
Download: 17fav Bookmark and Share WP Plugin Download.
Description: With this plugin you can send and share your favorites posts (your readers can do this too) to popular social bookmarking services like Digg, Meneame, Delicious, Technorati, Yahoo, Google, etc.
This plugin adds an friendly bar at the bottom of your posts, it means that is only visible when you are in a single post page, and it works like this because the page could turn slow if you have many posts in the main page (that means, higher loading time for the images).
Download: KnxDT Bookmarks WP Plugin Download.
Description: Gregarious is a social bookmarking plugin that integrates the new Digg API and Alex King’s Share This plugin, as well as the Reddit button and Feedburner’s Feedflare into one powerful, easy to use package. The AJAX interface makes customization a breeze, and the options put you in control. Gregarious works on a module based system, which means that it can have as many or as little features as you like.
Download: Gregarious WP Plugin Download.
Description: Hey Social is the coolest way to interact with the visitors of your blog, so that they can submit your posts and pages to the most famous Social services, such as Digg, Twitter, De.licio.us and so on.
Download: Hey Social WP Plugin Download.
Description: Social Bookmarking RELOADED – Add the social bookmarks services’s icons to your articles in your blogs in order to submit them easily. Plugin based on Apostolos Dountsis one.
Download: Social Bookmarking RELOADED WP Plugin Download.
Description: This plugin displays several social bookmarking options in a dropdown. Unlike other social bookmarking displays, this does not cause clutter.
Download: Social Dropdown WP Plugin Download.
Description: Social Links is a sidebar widget that displays icon links to your profile pages on other social networking sites.
Download: Social Links WP Plugin Download.
Description: This plugin is for bookmarking your post into stumble,technorati, digg and delicious. You have to do nothing but just activate the plugin. It automatically add the bookmarking options just below to your posts.
Download: addtothis WP Plugin Download.