Shareaholic is the simplest way to share, spread, and save interesting webpages via your social networks, email, blogs, IM, and more.
From Shareaholic
What is Shareaholic?
Shareaholic is a browser tool that makes sharing web pages in different platforms easy.
Shareaholic says in the wordpress.com forums:
- Our browser extensions (listed on http://en.support.wordpress.com/apps)
Shareaholic for Firefox, Google Chrome, etc is the easy way for YOU to share, spread, and post interesting web pages via blogs, right from your web browser. Works with all WordPress.com and WordPress.org blogs.
- Plugin for WordPress.org blogs to let your visitors share your content
http://wordpress.org/extend/plugins/sexybookmarks/
http://sexybookmarks.shareaholic.com/documentation/faq (extensive documentation)
We do not currently support WordPress.COM blogs. But this should change soon!
Mark the last part of the quote. It says Shareaholic currently does not support wordpress.com blogs. And that part is history already! 
Now it is possible to add Shareaholic in a wordpress.com blog post and that too in ONE click! The Shareaholic button will take your visitor to a Shareaholic page that has a wide range of sharing options.
To add Shareaholic in a wordpress.com blog post, you simply have to go to the link below and grab a bookmarklet:
Shareaholic bookmarklet for wordpress
Grabbed the bookmaklet? Cool! Now it’s time to learn how to use it and also to know why you may want to use it instead of other social bookmarking options. To get enlightenned, just…
Reporting that Chrome and the bookmarklet are consummating a happy marriage
Tried it and had no problems whatsoever. Thanks for sharing this 
Thanks so much for testing it in Chrome! And thanks for thanking me!
You are always welcome!
You can try make Facebook page for it and starts with your friends join it. Twitter can be useful, too.
I use Shareaholic on my work blog, http://blog.emptylemon.co.uk/, and think that it is by far the best social book marking tool out there. It looks awesome. I’ll try this work around for my wordpress.com blog later, thanks for sharing!
Reporting that Chrome and the bookmarklet are consummating a happy marriag…