Press This provides a lightning-fast way to grab text, images, or video from any website and post it to your blog without ever visiting WordPress. You can also use Press This to quickly share a link on your blog.
It only takes a second to get the Press This mini-application going. Simply go to Tools -> Tools in your dashboard and find the link to the bookmarklet:

Next, drag the Press This link to the bookmarks/favorites area of your web browser. (It may look different than what’s pictured below, depending on your browser.)

That’s it – you’ve installed Press This!
Using Press This
Let’s say you come across a great blog post about landscape photography, and you want to quickly share a few of the author’s tips with your own blog readers, without reproducing the entire post. Simply highlight the material with your cursor and then click the Press This bookmarklet in your browser.
Or maybe you just want to quickly share a link to a website, without reproducing any of the content in your own post. In that case, just click the Press This bookmarklet while you’re viewing the webpage.
Press This will appear in a pop-up window. You’ll have the option to add images, video, and/or your own commentary to the post before publishing it to your blog. If you have multiple blogs, use the drop-down menu to choose where to publish the content.

Adding Images and Video
To include images, click the picture frame icon. You’ll see a selection of all the images from the webpage. Select the one you like and click Insert Image. If you like, use the HTML tab to edit it. Use the filmstrip icon to add video.

via Press This « Support — WordPress.com.