We prefer share this. They provide GA integration, tracking of click throughs/shares, customization of icons, easy wp plugin installation, and several options for default styling & positioning. Plus they have something like 200+ networks available to choose from & it's FREE!
There's a lot of Free Social Bar in WordPress.org actually. Try these plugins like social bookmark.. Quite user friendly
The two best, in my opinion, are Digg Digg and Sharebar: http://bufferapp.com/diggdigg http://devgrow.com/plugins/sharebar/
Just to confuse the issue I will throw a big shout out to sexy bookmarks you can see it in action on my blog http://technicalnotebook.com the thing I like is that it offers options for just about every social bookmarking/sharing site you could think of. Plugin page is at http://wordpress.org/extend/plugins/sexybookmarks/ as I said I am a huge fan and really easy to se up as well which is a bonus. Stu
Plugins help to ensure that your WordPress blog runs at peak performance and those that allow you to make that happen are the best WordPress plugins 2012. Among the many plugins available, there are those that can be considered as the best WP plugins as they are destined to be popular due to their functionality.
Share This is what we use for our clients on over 500 websites, I use the option where you dont allow it to work on pages since most content that needs to be shared is for posts mainly. Hope this helps.