I noticed Add This when I tried the share buttons on an article I read on the Internet. I was hoping Add This might be like Reblog in WordPress, but it is not.
On one level, Add This is like Press This. If you come across an article with an Add This share box (it is an orange button with a plus sign and the word share in it), you select WordPress, and another box that asks for your WordPress blog URL opens up. You enter the URL of your blog, and you end up with a blog post with the title of the article and a link. Here is an example:
Another positive aspect of using Add This is that it works more easily in Internet Explorer than Press This does.
In addition, Add This installs share buttons on your blog. You can see what they look like in the right column of my blog. One of these buttons is an Add This button (an orange button with a white plus sign on it). If you press this button, a separate window like the one below opens and gives you many social media options to choose from.
The instructions for installing Add This vary depending on what type of WordPress blog you have. An Add This plugin is available for custom blogs. For free WordPress blogs, Add This can be added through the Text widget. In this widget, you have to include the Add This button code. There is also code available for blogs with WordPress.com VIP hosting. The codes and the instructions for these installation methods are located on the Add This Support Page.
Add This seems to be a handy tool to have whether or not you are deeply involved in social media, and it is easy to install on your blog as well.