I've been using the Zemanta plugin for a long time, and absolutely adore it! It helps my readers by identifying relevant Wikipedia entries (or direct site links) for words contained in posts. It searches the web for relevant (and appropriately licensed for sharing) photos and graphics, for when I don't have an image ready to include. It finds other relevant posts from the blogosphere to include at the end of my posts--another help for readers, and a way to connect with other writers with my interests. Finally, it will help identify appropriate tags, to make my content that much more visible in searches.
I'm in control of all of these links. I decide what works in my post, not Zemanta. And it's easy to work with. You'll love this!