Zemanta is not as powerful as the imaginary Google Writer envisioned last year for April Fools Day. It's a tool that helps bloggers writer better articles by suggesting related content from the web. You need to install a Firefox extension and it automatically shows related images, blog posts and Wikipedia articles next to the post editor. The nice thing is that Zemanta dynamically adjusts the suggestions as you add more content, but the suggested links aren't always helpful, as you can see in the screenshot below:
Zemanta suggests that the algorithm for finding recommended content is complicated, but it seems to rely mostly on identifying concepts and proper nouns. "We analyze your post through our proprietary natural language processing and semantic algorithms, and statistically compare its context framework to our preindexed database of other content."
The tool should do a better job at detecting the important keywords from the text and should allow users to provide feedback for the suggested links. For now, it's a pretty cool way to find blog posts related to your articles, but I wouldn't be surprised if this will evolve into a clever blog editor.