Yesterday I attended a presentation of Zemanta, a recently launched "blogging apprentice".
Currently only a Firefox plugin ( IE on the way, if anyone cares ), running on Blogger, Typepad and WordPress < 2.5. Its concept is simple: It gets the images from Wikimedia Commons, Flickr and various stock photo providers, and lets you pick them out and place them into your post. They are suggested based on contextual comparison of your text and the image's title, description and articles they were used in originally.
From what i used it, i was satisfied. Looking forward for the WordPress 2.5 update.
Update:
Zemanta now works with WordPress 2.5, and i seem to have played my part in it =D