You can see a "BlogThis!" button in the blogger official share buttons set.When other blogspot user click on this "BlogThis" button,he/she can share your blog posts easily through Blogger.

But if you want to add this "BlogThis" feature to your blogger blog as a Text Link,then this tutorial will helpful for you.

What is BlogThis! ?

BlogThis! is an easy way to make a blog post without visiting blogger.com. Once you add the BlogThis! link to your browser's toolbar, blogging will be a snap. Or rather, a click. Clicking BlogThis! creates a mini-interface to Blogger prepopulated with a link to the web page you are visiting, as well as any text you have highlighted on that page. Add additional text if you wish and then publish or post from within BlogThis!

From Blogger Help

Now follow the steps given below to add "BlogThis!" feature as a text link to your blogspot blog.

1.Login to your blogger Dashboard--> Design- -> Edit HTML

2.Click on "Expand Widget Templates"

3.Scroll down to where you see below code:

<data:post.body/>

4.Now copy the code given below and paste it just before the <data:post.body/>.

<b:if cond='data:blog.pageType == &quot;item&quot;'>
<div style='float:right;margin-right:10px;'>

&lt;a href=&quot;javascript:popw=&#39;&#39;;Q=&#39;&#39;;x=document;y=window;if(x.selection) {Q=x.selection.createRange().text;} else if (y.getSelection) {Q=y.getSelection();} else if (x.getSelection) {Q=x.getSelection();}popw = y.open(&#39;http://www.blogger.com/blog_this.pyra?t=&#39; + escape(Q) + &#39;&amp;u=&#39; + escape(location.href) + &#39;&amp;n=&#39; + escape(document.title),&#39;bloggerForm&#39;,&#39;scrollbars=no,width=475,height=300,top=175,left=75,status=yes,resizable=yes&#39;);if (!document.all) T = setTimeout(&#39;popw.focus()&#39;,50);void(0);&quot;&gt;BlogThis!&lt;/a&gt;

</div>
</b:if>

5.Save your template.Now you can see a "BlogThis!" link in your every blog post(not homepage).