If you’re on Google+, SocialStatistics.com can help you know how many people are paying attention to you and how fast that number is growing.
Google Ripples is a tool built into Google+ that maps how many times your posts are shared, and who is sharing them. Its visual design makes it kind of hypnotizing!
Twitter Counter will let you know how you rank against other tweeters and what your growth in followers is like.
If you’re a dedicated Facebook user (there are a few!) Insights is the Facebook tool to let you know how welled “Liked” your page is.